From the theoretical and empirical aspects, this paper studies the influences of IPO on the equilibrium value and the differentiated product market competition of peer listed companies. Improving existing studies by introducing the information spillover effect, a differential game model is developed based on dynamic product market competition. Our model shows that the equilibrium value decreases if a firm's relative competitiveness is less than the critical value after IPO, while its equilibrium value increases if its relative competitiveness is greater than the critical value before IPO. Based on the data of the small and medium plates, GEM, and all listed A shares, the differentiated product market competition after IPO is studied by using nonlinear least squares to estimate dynamic structured model parameters. The empirical results show that firms after IPO tend to enjoy higher consumer loyalties, that the product market competition tends to be heterogeneous, and that more market shares are converted into profits, which suggests that the competition effect of IPO is dominant. Moreover, IPO poses a threat to listed companies, and forces them to adopt differentiated product competition strategies to improve their competitiveness and profitability.