To investigate the impact of enterprise digitization on investment efficiency, this paper conducts an empirical analysis with a sample of A-share listed companies in Shanghai and Shenzhen from 2004-2021 to test the relationship between enterprise digitization, overhead rate and investment efficiency. It is found that: first, enterprise digitization is beneficial to enhance investment efficiency, and the conclusion still holds after a series of robust tests; enterprise digitization plays an enhancing role in investment efficiency by reducing overhead rate, i.e., overhead rate has a mediating effect in the effect of enterprise digitization on investment efficiency. Second, the effect of enterprise digitalization on investment efficiency is more significant in state-owned enterprises than in non-state-owned enterprises, and the effect of enterprise digitalization on investment efficiency is more significant in enterprises with two separate positions than in enterprises with two separate positions. The article examines the mediating effects of enterprise digitization on investment efficiency based on the perspective of overhead rate, enriches the study of economic consequences of enterprise digitization, analyzes the heterogeneity of property rights nature and two-job unity, and expands the related field research.