Whether it is“reducing debt”or “increasing equity”,deleveraging policy would boost ownership concentration, which will help overcome the actual controller’s free-riding behavior and restrain the management’s shirking behavior. Therefore, deleveraging policy might reduce the financial risk of enterprises. Based on the relevant data of all A-share listed companies in China from 2014 to 2019, the DID model was used to test the impact of deleveraging policy on the financial risk of companies. The results indicates that deleveraging policy can significantly reduce the financial risks of companies, especially for non-state-owned enterprises and listed companies on the main board. The mediating effect test shows that ownership concentration plays a part of mediating role in the policy effect. Therefore, it is suggested that enterprises should moderately centralize the ownership of the company in the process of deleveraging so that the financial risk can be reduced.