Abstract: Cooperation between enterprises is the key to the healthy development of enterprise clusters.Implicit contract accepted by cluster enterprises can inhibit opportunistic behavior,but it is also hard to protect stability cooperation from the perspective of game theory. This paper analyzes the tit-for-tat strategy in infinite repetitive prisoner dilemma game,and makes a conclusion that it is necessary to achieve stability cooperation to take the tit-for-tat strategy as the implicit contract,and to combine formal regulatory mechanism in enterprise clusters. This paper also gives recommendations of implicit contract in enterprise clusters and the formation of formal regulatory mechanism.

Key words: enterprise cluster, cooperation, implicit contract, norm