Abstract: The system of leniency based on peccavi, as a top-level design from judicial reform, aims at corresponding with the multi-value pursuit of criminal procedure, conveying the tolerance spirit and humanism. During the practice, the sincere peccavi of the accused makes the logical starting point, which reflects the utilitarianism and activism on the penalty and criminal litigation. The system of leniency based on peccavi emphasizes the close attention to the punishment of criminals, the protection of victims, the restoration of social relations, and the prevention of crimes in the long term. The system of leniency based on peccavi has the value of the times both internally and externally, perfecting the penalty theory from the intrinsic value, and practicing the litigation from the external value. The individual who chooses peccavi should discard rights partly, to satisfy the comparative benefits. The system of leniency based on peccavi should rely on the underscore justice that due process, which needs the effective participation and substantial effect, needs to perfect the information symmetry, the expression of pros and cons, legal help, compulsory measures and so on.