Abstract: The leniency or harshness in the enforcement of China’s antitrust law has been widely regarded as a focus of debates. The existing literature shows that there is not yet a normalized and systematic research on such issue. By introducing the concepts of positive and negative costs of antitrust enforcement, this paper sets up a model to decide the optimal law enforcement standard, which can establish the standard to measure the changes of antitrust enforcement. Through the analysis of the influencing mechanism of different variables on the optimal enflrcement standard, it can be seen that the leniency or harshness of the standard of antitrust enforcement is subject to such influencing factors as market environment, legal system, enforcement input, efficiency of enforcement, and benefit of enforcement. The major reason why China’s present antitrust enforcement is relatively lenient is that the enforcement lacks sufficient supply capacity with such characteristics as constitutive property, relativety and stage. At the present stage, China’s antitrust enforcement should adopt a moderate policy mix tool, enhance the ability of antitrust enforcement, establish a coordinative mechanism for the enforcement agencies, construct the classfied supervision system for the antitrust and regulated industries, and dilute the function of anti-administrative monopoly.

Key words: antitrust enforcement; fault cost; enforcement standard; analysis of the economics of law