Based on the audit cost-benefit theory and audit risk premium theory, the data of China's A-share listed companies from 2015 to 2020 are used as samples to test the relationship and internal mechanism between the leverage increase of controlling shareholders and audit pricing. The results show that the leverage increase of controlling shareholders is positively correlated with audit pricing. The leverage increase of controlling shareholders mainly promotes audit pricing through increasing the risk premium of auditors and increasing audit input. The above relationship is strengthened when the enterprise has the controlling shareholder's equity pledge and the legal environment is relatively strict, and better information disclosure quality and higher equity checks and balances would weaken the positive correlation. At the same time, the risk premium effect brought about by the leverage increase of the controlling shareholder will inhibit the auditors from issuing standard audit opinions and damage the audit quality. The conclusion helps to strengthen the risk perception of the controlling shareholders' leverage increase, and provides incremental evidence for further improving the quality of audit reports and strengthening investor protection.