According to the non-linear ship tracking control system, virtual control variables and Lyapunov functions are designed based on the Back-stepping and Lyapunov stability theory. A Nonlinear trajectory-tracking control algorithm is proposed, and a nonlinear trajectory-tracking controller is designed based the algorithm and LOS guidance law. The paper uses MATLAB Simulink toolbox to establish a nonlinear hydrodynamic model, and takes advantage of the simulation platform to validate the control law. The simulation results validate that the LOS guidance law can guidance ship to the expected way-point and the control law is able to control the system get a global asymptotic convergence. Numerical simulation shows the effectiveness and strong robustness of the control law proposed in this paper.