Abstract: The rule of invalidity of illegal contracts refers to the situation in which the imperative rule itself contains legal consequences. When the legal consequences of invalid contracts go against the principle of good faith, the basis for the applicability of the principle of good faith to the invalidity rule of illegal contracts includes 2 aspects: first of all, the principle of good faith and the rule of invalidity of illegal contracts are in conflict with the normative effect in the same case; in the second place, the scope of the corrective function of the principle of good faith can cover the unfair legal consequences of the invalidity of illegal contracts. Existing unilateral interpretation approaches approach centered on the principle of good faith should be established. In judicial practice, the key to the correction of invalid consequences of illegal contracts by the principle of good faith lies in finding the core points of the case and the conditional priority relationship. The corrective steps for the invalidity of an illegal contract by the principle of good faith can be summarized as follows: first, find out whether the parties concerned have violated the principle of good faith; second, weigh the importance of the realization of the principle of good faith and the rule of invalidity of illegal contracts in individual cases; third, test whether this priority relationship can be generally accepted.