This paper takes A-share listed companies from 2016 to 2021 as the research object to empirically test the relationship between key audit matters and asset mispricing. The results show that key audit matters can significantly alleviate asset mispricing, and information transparency and investors' irrational behavior play an intermediary role between them. Further research shows that the mitigating effect of key audit matters on asset mispricing is more significant in areas with better legal system and enterprises with high concentration of equity. This paper enriches the research in related fields, and provides reference for the government to improve the disclosure system of key audit matters for mitigation of asset mispricing and promote the high-quality development of the capital market.