A backstepping nonlinear robust control method is proposed to overcome the shortcomings of unmanned control ability, nonlinearity and strong coupling of flying wing UAV. This improved Backstepping method, which not only eliminates the influence of nonlinearity, but also guarantees the stability and robustness of the system. This method breaks through the limitation of many robust design methods that the upper bound of uncertainty norm is known, makes full use of the known uncertainty information of the system to improve the performance of the system, and solves the singular value calculation and conservation problems of the traditional Backstepping method. The simulation results show that the control method is reasonable and effective.