With the advantages of flexible deployment and configuration, fast response, and strong environmental adaptability, UAV aided communication has important applications in temporary hotspot areas, edge areas, and emergency communication scenarios. Compared with traditional wired backhaul links from ground base stations, considering the high mobility of UAV base stations, this paper considers a UAV aided communication system using in-band backhaul technology to maximize the minimum reachable rate of ground users by jointly optimizing the hovering position, bandwidth allocation, transmit power and user association of UAVs. To address this problem, an multi-coding artificial bee colony algorithm is proposed in this paper to solve the proposed joint optimization problem, extending the dimensionality of the search performed on the solution space. Simulation results show that the proposed multivariate coded artificial bee colony algorithm can achieve significant rate gain and improve the minimum reachable rate of ground users in UAV aided communication systems within a limited number of iterations compared to the block coordinate descent method.