An underactuated unmanned surface vehicle, as an important platform working in the sea or lake, has a wide range of applications. Motion control of an underactuated unmanned surface vehicle is researched. Firstly, the kinematics and dynamics model considering the wind and sea wave disturbance is built, and the nonlinear state equation is derived. Then the combination control algorithm of the sliding mode control based on exponential sliding surface and backstepping control is designed for heading controller. Finally in the simulations and experiments, the validity of the dynamics equation and the control algorithm designed in this paper is verified.