This paper examines the relationship between the defined benefit pension (DB plan) and the efficiency of the enterprise investment, thus revealing the corporate governance role of defined benefit pension in China. In this paper, we use the manually collected data of A-share listed companies participating in the DB plan from 2013 to 2016, and select the sample of the control group for the enterprises that implement the DB plan by the trend score matching method to control the sample self-selection problem. The results of the empirical test show that companies with DB plans have higher investment efficiency than those who do not implement the DB plan. In this paper, the test of two possible mechanisms of action found that DB plan to reduce the efficiency of inefficient investment is more obvious in the more serious group of shareholders’ agency conflict, indicating that it plays a role through the incentive mechanism; in the more serious group of bankruptcy threats, DB plans to reduce the efficiency of inefficient investment is more obvious, indicating that it plays a role through the benefit convergence mechanism. This article is of great significance for further understanding of the implementation of the DB program.