Based on the data of the 17 provinces and cities along the “Belt and Road” from 2003 to 2017， this paper uses an input-oriented three-stage DEA model to measure the green investment efficiency level of each province and city， and analyze the environmental factors affecting the investment efficiency level. The empirical results show that the current green investment in the provinces along the “Belt and Road” is generally inefficient， and the measurement results in “Silk Road Economic Belt” provinces and cities are lower than the overall average， and the measurement results in “Maritime Silk Road” provinces and cities are higher than the overall average. After eliminating the impact of environmental variables and random factors， the level of green investment efficiency has increased， indicating that existing environmental factors have an impact on investment efficiency. The lack of pure technology efficiency and scale efficiency will lead to low efficiency of green investment in China. What’s worse， the low level of technical management， the failure of optimal allocation of industrial structure and the unreasonable allocation of resources will lead to the problem of excessive consumption of resources investment， thus reducing the efficiency of green investment.