In this paper, we use a distinct quasi-natural experiments to examine the effect of liberalization of the stock market on corporate environmental, social, and governance(ESG) disclosure quality. We find that the liberation of the opening of Shanghai(Shenzhen)-Hong Kong Stock Connect (SHSC) significantly and consistently improves ESG disclosure quality of listed companies, and this effect is most evident in environmental information disclosure. We then find that the SHSC can improve the quality of ESG disclosure of listed companies through “voting with feet” and “external supervision” effect. Furthermore, the effect is stronger in firms that are Non-SOEs and with low equity concentrations. Overall, our results suggest that the liberalization of stock market can improve the quality of companies’ ESG disclosure quality.