An adaptive ship course following control law is proposed in this paper. Backstepping technology is employed as the main control framework. A sufficiently smooth projection operator and Nussbaum function are used to overcome the parameter uncertainties and unknown direction of control gain respectively. An auxiliary design system and Gaussian error function are utilized to tackle the limitation on rudder angle. The proposed controller can make the course tracking error be arbitrarily small by selecting appropriate design parameters and guarantee all signals in system to be uniform ultimate boundedness. Two simulation results show and verify that good dynamic performance can be obtained.