Identifying key audit quality factors and providing improvement paths in China’s capital market are crucial for audit research and high-quality market development. This study constructs an audit quality impact strength index from three dimensions: audit subject, object, and environment, combining statistical and economic significance. Utilizing data from all A-share listed companies spanning the years 2013 to 2021, it finds that in the audit subject dimension, moderate audit fee increases and auditor tenure extensions improve quality, while long tenures (over 4 years) harm it. In the audit object dimension, long-listed and loss firms have lower quality, while cash-rich and state-owned firms have higher quality. Media reports enhance audit quality in the environment dimension. Further analysis shows that moderate auditor tenure extension and fee increases are the most positive factors, while the long listing years, aggressive development and losses are the most negative factors.