There will be multiple photo voltaic（PV） users in the same distribution network area， and building a PV user group is one of the effective ways to manage them. In order to further promote the stability and development of the PV user group， it is necessary to evaluate the importance of users within the group. This paper analyzes the nature of the operator's revenue for the PV user group that implements the internal electricity price， and proposes a method for calculating the contribution value of the user to the operator's revenue based on the cooperative game theory. From the three aspects of users， operators and power grids， the importance evaluation indicators of users are defined， and then the importance evaluation and ranking of users in the PV user group are carried out based on the TOPSIS method in multi-criteria decision making. Simulation examples verify the effectiveness of the comprehensive evaluation method.