Based on the A-share listed companies from 2007 to 2018, this paper empirically examines the impact of biological assets on audit fees and its mechanism. The research shows that compared with the listed companies without biological assets, the audit fees of the listed companies with biological assets increase significantly, and in the listed companies with biological assets, the audit fees of the listed companies with biological assets impairment will be higher. The reason is that the biological assets have the characteristics of biological transformation, which increases the space of earnings management, and for the sake of audit cost and audit risk, the auditor will increase the audit fees. Further research finds that when the internal control of the enterprise is defective or the enterprise is a non-state-owned listed company, the positive impact of biological assets on audit fees will be more significant, furthermore, auditor industry specialization restrains the positive relationship between biological assets and audit fees.