This paper studies the problem of course keeping control for unmanned surface vehicle (USV) with servo dynamic characteristics, environmental disturbances and model’s uncertainties, and rudder saturation. Considering the characteristics of the rudder servo system (RSS), a nonlinear Norrbin model with second-order rudder is reconstructed, and proposes a finite time simple and practical course controller by the finite time dynamic surface control (FTDSC) technology, which achieve excellent finite time command filter. Then, the nonlinear disturbance observer (NDOB) is applied to estimate the lumped disturbances, which is easy to implement in engineering. Meanwhile, the bandwidth between the controller and the observer is studied, which affects the convergence speed of the observer. Besides, finite time dynamic auxiliary systems with smooth switching function (FTADS-SSF) is designed to compensate for rudder physical constraints with finite time convergence. Further practical finite time stability analysis indicates that the entire system is uniformly ultimately bounded (UUB). Finally, simulation comparison results have been demonstrated the proposed strategy.