Abstract: Multi-body aircraft is a new concept aircraft consisting of multiple small unmanned aerial vehicles hinged-connected by wing tips. This concept aircraft can integrate the performance and advantages of two types of flying platforms: small unmanned aerial vehicles and high-altitude long endurance unmanned aerial vehicles. It has great development potential. Based on the Newton-Euler equation and on the lifting line method, it establishes a multi-body aircraft flight dynamics model, and analyzes the trim and stability characteristics of the multi-body aircraft system that allowing the relative degree of freedom of rolling motion with the dual-aircraft combination. The results show that, different from the traditional configuration aircraft, the multi-body aircraft system has an unstable relative motion flight mode, which is dominated by relative rolling motion. This configuration aircraft cannot fly stably in an uncontrolled situation. Based on the completion of the dynamics modeling, the Proportion-Integration-Differentiation control method is used for stable control. The stable control loop is designed separately for each single aircraft to achieve the purpose of stable flight. The simulation results show that the control method is effective and can quickly stabilize the divergent flight dynamics system.