Abstract: Under the background of the rapid development of market economy, strategic alliance enterprises have been paid more attention by enterprises in the form of resource sharing and knowledge learning. The technological distance and social distance between strategic alliance enterprises have a direct impact on the knowledge flow within the alliance and the emergence of enterprise’s radical innovation. Enterprises and their own knowledge protection ability have a certain impact on the efficiency of knowledge flow between different organizations and enterprises and the success of radical innovation. Therefore, it is significance to clarify the impact of organizational distance between strategic alliance enterprises (including technological distance and social distance), knowledge flow (including knowledge acquisition and knowledge leakage), and knowledge protection ability on the radical innovation of alliance enterprises to promote the continuous realization of new breakthroughs by enterprises.This paper firstly defines and analyzes the relevant theories and concepts of organizational distance, knowledge flow, radical innovation and knowledge protection abilityamong strategic alliance enterprises based on the literature review at domestic and abroad. The organizational distance is divided into two dimensions of technical distance and social distance, and the knowledge flow is divided into two dimensions of knowledge acquisition and knowledge leakage. Then proposes seven groupsof hypotheses: H1a: The farther the technological distance is, the more favorable it is for alliance enterprises to make radical innovation. H1b: The closer the social distance is, the more favorable it is for alliance enterprises to make radical innovation. H2a: Knowledge acquisition positively influences the radical innovation of alliance enterprises. H2b: Knowledge leakage negatively affects the radical innovation of alliance enterprises. H3a: The farther the technology distance is, the more conducive it is to knowledge acquisition between alliance enterprises. H3b: The more distant the technology is, the less conducive it is to knowledge leakage between alliance enterprises. H4a: The closer the social distance is, the more conducive it is to knowledge acquisition between alliance enterprises. H4b: The closer the social distance is, the less conducive it is to knowledge leakage between alliance enterprises. H5a: Knowledge acquisition will mediate the relationship between technological distance and radical innovation. H5b: Knowledge acquisition will mediate the relationship between social distance and radical innovation. H6a: Knowledge leakage will mediate the relationship between technological distance and radical innovation. H6b: Knowledge leakage will mediate the relationship between social distance and radical innovation. H7a: Knowledge protection ability negatively regulates the relationship between knowledge acquisition and radical innovation. H7b: Knowledge protection ability negatively regulates the relationship between knowledge leakage and radical innovation.Next, on the basis of exploring the correlation between the variables of each dimension,a research hypothesis was proposed, and the conceptual model with joint action and knowledge protection ability as the moderating variables was established. The object of this study is strategic alliance enterprises in China. In order to ensure the accuracy of measurement, mature scales studied in relevant fields at home and abroad were selected as far as possible, and the expressions used in Chinese literatures were used for reference in the classical scales in foreign literatures. On this basis, improvements were designed. Before the formal investigation, 100 domestic enterprises were randomly selected as samples to issue the questionnaire. Based on the feedback results, the questionnaire was further improved and the final questionnaire was determined. From July to August 2017, 774 questionnaires were officially issued, 471 of which were valid, with an effective rate of 60.85%.The surveyed enterprises are evenly distributed geographically, most of them have been established for more than 6 years, and most of the respondents are senior managers. The survey is representative to some extent. Finally,in order to answer the question of how the organizational distance of alliance enterprises under the knowledge protection capability and the knowledge flow between them can promote the radical innovation, as well as the regulating role of knowledge protection capability. Based on knowledge management theory and resource-based theory, this paper proposes 7 sets of hypotheses and uses data from 471 strategic alliance enterprises to test the hypotheses. The results show that: (1) The technological distance and social distance between strategic alliance enterprises are conducive to the radical innovation of alliance enterprises. A certain technical gap and intimate relationship between partners within the alliance can help each member integrate the internal knowledge of the alliance with the enterprise’s own knowledge so as to develop new products and technologies. (2) The knowledge flow in the organization innovation breakthrough type in relation to the distance of partial intermediary role, in the league has different technical levels and the relationship of the cooperative enterprise will continue to increase the knowledge acquisition of internal finally realize its own radical innovation, but also can leak by lowering their own knowledge, the uniqueness of protection applied in the innovation of core knowledge, promote the breakthrough "innovation and development. (3) The knowledge protection ability of enterprises will weaken the negative effect of knowledge leakage on radical innovation, but it will not significantly weaken the promotion effect of knowledge acquisition on radical innovation.The research conclusion of this paper has a guiding significance for alliance enterprises radical innovation, through the organization of distance, knowledge flow and radical innovation three relations research, guide enterprises in selecting the appropriate technology gap in the league and close partners, promote the union both knowledge exchanges, mutual benefit and win-win results, a radical innovation and sustained development. Secondly, the analysis of the results of knowledge flow can guide enterprises to correctly view the different forms of knowledge flow within enterprises in the process of cooperation, and make full use of the positive role of knowledge leakage while acquiring and creating new knowledge to achieve radical innovation. Finally, according to the relevant research conclusions, it guides strategic alliance enterprises to continuously enhance their knowledge protection ability in the process of cooperative development, and promotes the application of property rights and institutional mechanisms in the field of enterprise knowledge protection in enterprise practice. Promote the mutual promotion of organizational distance, knowledge flow and radical innovation within the alliance, realize the common development of the alliance enterprises, and constantly create new competitive advantages to achieve sustainable innovation and development.

Key words: technical distance, social distance, knowledge acquisition, knowledge leakage, radical innovation, knowledge protection ability