Abstract: A multi-UAVs coupled cooperative formation control method was proposed based on leader state estimation to solve the problem of large leader communication load and the lack of dynamic performance due to the multi-UAVs coupling. First, a leader-state estimation method was proposed. And then, a-leader state observer was designed for each UAV in the formation to achieve real-time estimation of the leader-state without direct information interaction between each follower and the leader, reducing the leader communication load and increasing the communication redundancy. Combined with the leader-state observer, a cooperative formation control method was presented for UAV coupling to achieve UAV trajectory control and analyze synchronously the effect of formation coupling gain on formation control. Finally, it was applied to trajectory tracking control. The simulation results show that the proposed method can accurately estimate the real-time state of the leader and accomplish the formation flight assignment of the UAV to maintain the desired formation, verifying the effectiveness of the proposed cooperative formation control method.