It is universally existed in Yangtze River Delta that the result of regional regulations conflict is rooted in "Externality" between different regional governments. The difficulties of coordinating regional regulations conflict lies in the tough works of voluntary negotiating which only can be facilitated if there were no external authorized participation. The conundrum of coordinating regional legal systems is that how to facilitate voluntary cooperation between local governments without external authority. The voluntary cooperation without external authority, according to the theory, depends on three key elements:Equal retaliation (uncooperative) capability; Game length of period; Reputation mechanism and the community of the three elements. Implications of the theory, in order to improve the coordination, local governments of Yangtze River Delta have to set up a special partner agency organizing the regional coordination, coordinate the normalization of regional regulations and use the reputation mechanism to operate the regional regulations coordinate smoothly, so that can achieve the "best" in the game of legislation and enforcement to solve the problem caused by regional regulations conflict effectively.