Taking all A-share IPO companies from 2018 to 2021 as the sample, this paper constructs a PSM-DID model to empirically study the impact of the registration system reform on the “performance deterioration” of IPO companies. Empirical research results show that the registration system reform can significantly reduce the “performance deterioration” of IPO companies, especially the “performance deterioration” of non-state-owned IPO companies and IPO companies audited by low-reputation accounting firms. Mechanism analysis discovers that it is through three mechanisms, namely restriction of earnings management, promotion of information disclosure, and devaluation of the shell of IPO companies, that the registration system reform reduces the “performance deterioration” of IPO companies after going public. This paper not only manages to assess in a new manner the policy effect of the registration system reform, but also provides theoretical references to relevant departments responsible for regulating the information disclosure of IPO companies.