UAVs carrying loads by single aircraft for transportation are limited in carrying capacity, and multi-copter integration is a general trend. In the traditional rotor-load model, the treatment of constraints for UAV hanging load calculation of multi-rotor aircraft synergism requires the introduction of multiple auxiliary variables, and the modeling process is relatively complex, and the analytical effect needs to be improved. It is an effective attempt with the Udwadia-Kalaba (U-K) equations dealing with both ideal and non-ideal constraints co-existing systems, modeling rotary-wing UAV cooperative flight control to solve the problem of rotary-wing cooperative load transport. By establishing the kinematics model and dynamics model of the rotary-wing UAV, using the U-K equation to deal with the motion constraints, the treatment divides the load"s influence on the UAV into horizontal and vertical directions, which is input as a step signal to solve the calculation, and the series-level PID control model is designed for the control strategy of the system, which ensures that the rotary-wing UAV under the condition of multi-aircraft cooperative has good anti-jamming ability and Stability. Simulation analysis is carried out using Simulink model in Matlab environment, and the numerical simulation results show that the proposed control method achieves the stability, speed and accuracy of the formation system, and can achieve the goal of optimizing the effect of rotary-wing UAV cooperative control.