Abstract: In order to implement straight-line trajectory tracking control for unmanned parafoil vehicles (UPV), a variable-gain robust backstepping control method was proposed based on a simulation object. A variable-gain baekstepping tracking controller was designed against the trajectory tracking error model, and proper design of gain parameters eliminated a part of complicated nonlinear terms and avoided higher derivatives in traditional backstepping methods so as to make the controller simpler and to be beneficial to engineering realization. The robust feedback compensation term designed according to the Lyapunov theory improved the system's robustness while ensuring its stability. In addition, the controller was applied to UPV planar straight-line trajectory tracking control. The simulation experiment illustrates the good robustness of the proposed controller and the accurate tracking ability in straight-line trajectories.