This study assesses the impact of market-oriented reforms of the Chinese initial public offering (IPO) system on investor speculation. The empirical results reveal that the registration-based IPO system reform expedites the release of investor sentiment and curbs speculation in the post-IPO period. The registration reform in the Sci-Tech Innovation Board (STAR market) is more effective than that in the Growth Enterprise Market (GEM), and the long-term effects surpass the short-term effects. Further tests indicate that greater institutional (individual) investor participation is the reason for higher (lower) reform efficiency; as investor sentiment increases, the dampening effect of the registration system reform on speculation decreases. Our study confirms the importance of market-oriented reform and provides implications for implementing efficient reforms in emerging markets with high levels of manipulation and speculation.