Using a quasi-natural experiment that mandates a subset of listed firms to issue corporate social responsibility(CSR)reports,this paper examines the effect of mandatory CSR disclosure on market information asymmetry in China,where we estimate information asymmetry using high-frequency trade and quote data.We find that contrary to the criticism that mandatory CSR disclosure lacks credibility and relevance in emerging markets,mandatory CSR reporting firms experience a decrease in information asymmetry subsequent to the mandate.In additional analysis we further find that this relation is more pronounced for firms with greater political/social risk and firms with less analyst coverage.