In view of the contradiction between system capacity and user fairness in the resource allocation of UAVbased communication links based on OFDMA, a new resource allocation algorithm is proposed .The algorithm is mainly composed of two parts, i.e. subcarrier allocation and power allocation. In the subcarrier allocation process, each subcarrier is allocated by equal power, and the fairness threshold is set to ensure that the user fairness is taken into account when maximizing the system capacity; In the process of user power allocation, the power optimization strategy based on the gray wolf algorithm is adopted, and the power allocation between users is realized through global search. The simulation results show that the proposed power allocation method based on gray wolf algorithm is characterized by robustness and optimization ability. Even in the case of a large number of users, the method can still maximize the system capacity while having high user fairness. At the same time，the relationship between system capacity and user fairness can also be flexibly adjusted by setting the size of the fairness threshold.