Abstract:     Industrial clusters not only aggravate competition among enterprises, but also promote cooperation among them. Cooperation can efficiently reduce the costs comprehensively, such as production, transaction, marketing and innovation fees, which will improve the overall competitiveness of enterprises, as well as the overall competitiveness of the whole industrial clusters. The coopetition relationship within industrial clusters is the core value of industrial clusters, and it is also the fundamental reason why industrial clusters are more competitive than any single enterprise. However, in fact, it is never an easy decision for enterprises to decide whether they should put themselves in a coopetition relationship, in the consideration of information asymmetry, development stage, external competitive environment and other factors. 
   This problem is particularly prominent when coopetition exists in the field of innovating activities. One of the reasons is the objective spillover of knowledge; another reason is the opportunistic risk brought by "learning competition". Both of them may lead to insufficiency and even serious missing of trust of cooperation, and therefore the spontaneous cooperation hardly happens among enterprises by the power of market only. In addition to the influence of the market itself or the government participating, there is a more powerful solution to deal with this kind of problem. We can introduce a third-party industrial cluster promotion institution, which may act as an intermediary. 
   Overall, research institution/university is one of the most ideal choices for industrial cluster promotion institutions. Because research institutions/universities have already mastered a large amount of innovation resources. More importantly, research institutions/universities have a relatively neutral status compared to most of the enterprises in the market. Therefore, letting research institutions/universities be the industrial cluster promotion institution will bring benefits mainly from the following two aspects. On the one hand, they can directly promote the innovation ability of industrial clusters; On the other hand, they can also indirectly promote the R&D cooperation of competitive enterprises, and then make the resources of various actors more and more concentrative, effectively solve the bottle-neck technical problem, and finally achieve the goal of improving the overall value chain status of the whole industry. 
  By taking the role of the promotion organization of the New Generation Information and Communication Industry Cluster in Shenzhen as an example, this paper studies the choice of competition and cooperation strategy among enterprises in the industrial cluster with the methods of combining theory and case analysis. During this study, we found out that in the process of cultivating industrial clusters into innovation clusters, the promotion institutions of industrial clusters mainly have three functions in both direct and indirect way. First of all, it is able to play an important role in improving the degree of heterogeneity. Secondly, it can also establish trust mechanism among the enterprises. Additionally, it can definitely support innovation activities. 
   Furthermore, this paper gives some enlightenment for the corresponding policy: firstly, it is important to provide a stable market environment for the development of industrial clusters. Secondly, guiding the direct participation of research institutions/universities in industrial clusters is also necessary. Finally, the atmosphere of encouraging enterprises to carry out multi-mode R&D cooperation with research institutions/universities should establish.

Key words:  industry cluster, coopetition strategy, trust mechanism