Virtual power plants (VPP), as an advanced technology that aggregates and optimizes the utilization of renewable energy, controllable load and energy storage system, can effectively promote the green and low-carbon transformation of power system. It is of great significance for the investment and operation of VPP to comprehensively evaluate the benefits of virtual power plants. This paper constructs a set of evaluation index system to comprehensively evaluate the economic, social and environmental benefits of VPP. The proposed approach can reasonably evaluate the value of VPP in terms of construction, power grid operation, energy conservation, emission reduction, and social effects. The benefit evaluation index system has been applied to a VPP application pilot, and the calculation process of its benefit evaluation index are elaborated in detail.