The movement of a double-frame aircraft skin inspection robot on the outer surface of the aircraft is discussed. Firstly, the movements of the robot are analyzed and divided into two types of the sliding gait and the rotational gait.Secondly, the single-step motion of the robot is regarded as the coupling of the sliding and rotational motion according to its mechanical structure.Then, in view of the single-step motion, a kinematic model of the robot is established, which includes a position dynamics model based on Cartesian coordinates system and a kinetic model based on the coupling of the rotation angle and the sliding displacement. Finally, in order to accomplish the robot's tracking movement on the outer surface of the aircraft, a sliding mode controller based on RBF adaptive compensation is designed.By using Lyapunov stability theory, the convergence of the tracking error is proved.Simulation results have verified that the aircraft skin inspection robot can realize the asymptotic tracking of the desired trajectory, and has a satisfying control performance.