In order to evaluate the comprehensive energy index of the UAV formation, a set of complete energy index for the problem of UAV aggregation is constructed. The process of UAV aggregation is analyzed, the index system and its mathematical model are established to evaluate the main performance of the UAV aggregation, such as rapidity, correctness, stability, security, survivability, emergency capability, and communication performance. The judgment for one aggregation task is given. The results show that the performance index system can cover the process of unmanned aerial build-up and has some reference value.