Unmanned aerial vehicles (UAVs) have the characteristics of high mobility, strong environmental adaptability and large business coverage. With the increasingly low cost of UAV and the continuous optimization of various performance, the cooperative communication of UAV equipped with micro relay has shown great advantages in the communication system. Therefore, UAV can be effectively applied to the integrated network of aerial terrestrial. Due to the proliferation of communication equipment, the communication environment is gradually complicated, there is co-channel interference at the relay and destination nodes of the UAV. In order to improve the utilization rate of spectrum resources and ensure the stability of signal transmission, the UAV relay with the highest end-to-end signal to interference plus noise ratio (SINR) is selected to transmit information to the destination node by decoding and forwarding protocol in the cooperative communication involving multiple UAV relays. In the presence of co-channel interference and the drone flying at high speed, we derive an exact expression of the system interruption probability and channel capacity. Theoretical analysis shows that increasing the number of UAV relays can compensate for the system performance degradation caused by co-channel interference and further improve the system performance.