Compared with the traditional PID control method, L1 adaptive control has an ideal control effect when the aircraft parameters change. In this paper, a lateral dynamic model of a certain UAV with parameter uncertainty was established. Based on the study of L1 adaptive control theory, L1 adaptive control law and PD control law were designed respectively. The control effect of these two control laws for the roll angle of UAV was compared and analyzed by simulation. The results show that the L1 adaptive control law has good anti-aircraft parameter change ability and strong robustness. It has important reference value for the design of UAV flight control system.