The investment and construction of new energy power generation projects is an important support for constituting a clean, low-carbon, green and efficient new energy system. In this paper, for the evaluation of investment decision of new energy power generation projects, the principle of combining quantitative and qualitative indicators was adopted to establish an index system that includes technical and economic benefits. On this basis, the weights of indicators were determined by entropy weight method (EWM), and the evaluation model based on technique for order preference by similarity to an ideal solution (TOPSIS) was established. The feasibility and effectiveness of the method of this paper were verified by the numerical tests on an IEEE 39-bus system. The results indicate that this method can comprehensively measure various indicator factors that affect the investment of new energy power generation projects, and can provide a reference basis for investment decision-making and evaluation of new energy power generation projects.