The leniency policy plays an indispensable role in thwarting cartel formation. To maintain the fairness of market competition, most countries successively bring this policy into their antitrust legislation. After the enforcement of the policy, the involved firms may have incentive to self-report and provide evidences to the Antitrust Authority. Therefore, the authorities can get enough evidence to convict those firms of being cartel members. In this paper, we develop two kinds of game theoretical model and use the concept of subgame perfect equilibrium and sequential equilibrium to discuss the efficiency of leniency policy in general conditions, and the effectiveness of the policy under the condition of information asymmetry. We show that it is efficient to the society and the authorities when the cartel members self-report under the enforcement of leniency policy. Moreover, by setting up an appropriate fine payment, self-reporting can be a signal for the authorities to segment the type of the involved firms.