This study selects samples of 2896 IPO companies in the A-share capital market in 1990—2015, and takes the IPO event as the research object. In this paper, the effect of IPO earnings transparency on investors’heterogeneous beliefs and the impact of the IPO system reform on this role are studied. The test results show that: First, we group the sample based on the mean and median of IPO earnings transparency variables and conduct a comparative test. In general, the results show that investors’heterogeneous beliefs in group with high IPO earnings transparency are significantly lower than those in group with low IPO earnings transparency. After controlling the influence of other factors, we find that IPO companies reduce earnings transparency by improving earnings manipulation through accounting policies and real activities, and with the decrease of earnings transparency, investors’heterogeneous beliefs are significantly improved. After extending the window period, the results show that the reduction of earnings transparency caused by IPO’s manipulation of earnings information through accounting policies and real activities significantly leads to the higher heterogeneity of investors’beliefs in the longer window period after IPO. Second, the IPO system reform at various stages has significantly affected the effect of IPO earnings transparency measured by accrual earnings management on investors’heterogeneous beliefs, but the effect of IPO earnings transparency measured by real earnings management and total earnings management on investors’heterogeneous beliefs is not significantly affected by the IPO system reform at various stages except the significant weakening effect of the reform from quota management to index management.　　This study shows that earnings transparency significantly affects the formation of investors’heterogeneous beliefs. The IPO system reform has played a certain moderating effect in this process. The overall performance of the IPO system reform is the improvement of the marketization of system implementation, which will gradually highlight the decisive role of the market in resource allocation, and enhance the correlation between the management information disclosure strategy and investors’decision-making. Investors’understanding and application of information directly affect the effectiveness of the capital market, and transparent information will help investors form a consistent understanding of the value of IPO companies and reduce transaction volatility. Therefore, in the process of the market-oriented reform of the IPO system, it will be one of the most important ways to stabilize the market volatility by improving information transparency to reduce investors’heterogeneous beliefs in decision-making.