Abstract: Nowadays, the new round of scientific and technological revolution and the accelerated transformation of China′s economic development pattern have formed a historic intersection, where opportunities and challenges coexist. However, most Chinese firms are in traditional industries and are at the middle or lower place of the global value chain. Compared with the firms of developed countries, Chinese firms still have some gaps in resource allocation, business development and industrial structure, which is rooted in the lack of innovation. Innovation, by changing the combination of essential productive factors, can improve the efficiency of resource allocation and stimulate the development of enterprises, and is the fundamental way to promote high-quality development of firms. Moreover, in the process of firm innovation, firms should not only pay attention to the single dimension of innovation input or innovation output, but also focus on the efficiency of transforming innovation input into innovation output. Therefore, the Government Work Report in 2019 pointed out that China should implement the innovation-driven development strategy and further improve the innovation capacity and efficiency. Accordingly, how to improve the innovation efficiency of firms is an important issue to be solved urgently now. According to the report to the 19th National Congress of the Communist Party of China, the focus should be on the Belt and Road construction to foster new advantages in international economic cooperation and competition. In 2014, the Belt and Road Initiative was transformed from top design into the actual implementation of national policy. Chinese firms positively response to the initiative, and play an important role in core technology fields, such as infrastructure construction, energy cooperation, industrial investment and the park construction, the international cooperation capacity when they cooperate with countries along the Belt and Road. The implementation of the Belt and Road Initiative has not only promoted the participation of Chinese firms in international economic cooperation, but also greatly promoted international technological exchanges and research and development cooperation, which provides an opportunity for Chinese firms to improve their innovation efficiency. Existing studies examine the influence mechanism of the Belt and Road Initiative mainly from risk undertaking, investment way and innovation demand of firms. However, the existing literature on the impact of Belt and Road Initiative on the innovation efficiency of firms is still not clear. In addition, firm innovation is characterized by large investment, high failure rate and long cycle, so it may take some time for the implementation of the Belt and Road Initiative to play a significant impact on the innovation efficiency of firms. Therefore, from the perspective of risk tolerance, this paper investigates the current effect, lagging effect and dynamic evolution effect of the implementation of the Belt and Road Initiative on firm innovation including innovation input, innovation output and innovation efficiency, in order to understand the influence mechanism of the Belt and Road Initiative on firm innovation efficiency. Based on the exogenous event of the implementation of Belt and Road Initiative in 2014, this paper takes Chinese listed firms engaging in outward foreign direct investment (OFDI for short) from 2011 to 2017 as the sample, and empirically tests the impact of Belt and Road Initiative on innovation efficiency of firms as well as its mechanism with difference-in-difference (DID) model. Firstly, the results show that in the short term, Belt and Road Initiative can significantly promote the innovation input of firms; in the long term, Belt and Road Initiative can also significantly improve the innovation output and innovation efficiency of firms. Secondly, the paper investigate the dynamic effect and finds that the positive impact of the initiative on firms′ innovation including innovation input, output and efficiency is annually increasing since the year of 2014. The conclusions remain stable after controlling industry and firm fixed effect. Finally, from the perspective of risk tolerance, the paper takes the factors of religious culture of host countries along Belt and Road and firm strategic decisions into the influence mechanism. The results show that Islam religious culture of host countries reflects their low level of risk tolerance, and thus the positive effect of "Belt and Road" initiative on innovation efficiency of firms is more significant in the non-Islamic countries. However, the firms′ diversified business strategy reflects their high level of risk tolerance, which increases the positive effect of "Belt and Road" initiative on innovation efficiency of firms.  The implications of the research are mainly in three aspects. Firstly, the research help us to understand the economic impact of the Belt and Road Initiative on innovation efficiency of firms. Firms are the main market carrier to participate in the construction of Belt and Road, relevant government departments should encourage firms engage to scientific and technological exchanges through economic cooperation along the Belt and Road route in order to carry out major scientific and technological breakthroughs through cooperation and jointly improve the innovation efficiency of firms. Secondly, because most countries along the Belt and Road have religious culture characteristics, Chinese firms should be "adjust measures to local conditions" in the process of participation in international economic cooperation. They should take the religious and cultural factors of host country into the risk tolerance analysis of host countries, in order to give full play to Belt and Road Initiative on innovation efficiency of firms. Finally, due to the long cycle and high uncertainty of firm innovation, it takes some time for firms to improve their innovation output and innovation efficiency. Therefore, in the process of participating in the construction of Belt and Road, firms should adopt diversified business strategies to improve the level of firm risk tolerance, in order to play a positive role of Belt and Road Initiative on the innovation efficiency of firms. Above all, the research not only affirms the positive effect of the implement of Belt and Road Initiative on innovation efficiency of firms, but also enriches the related studies in the field of Belt and Road Initiative and firm innovation efficiency. The research provides important theoretical implications and practical references for promoting high-quality development of Belt and Road cooperation and further turning China into an innovation-driven country.

Key words: Belt and Road Initiative, innovation efficiency of firms, risk tolerance, religious culture, business strategy