An algorithm of path following for Unmanned Underwater Vehicle (UUV) based on backstepping is proposed in this paper. To design the path following controller by the backstepping technique, the algorithm compares desired path predefined and the path information collected from the sensors of vehicle and combines with Lyapunov theory analyzing the stability of the control system. The path following method for the vehicle with two inputs and three outputs in the horizon plane has been clarified. The sway coupled virtual control input is introduced. The aim for the controller designed is to drive the real location and orientation tend to the desired path information, to guide the whole velocity inclining to the tangent of desired path, and to guarantee the heading asymptotically converging to zero ultimately. Lake experiment data shows the validity of the method presented.