Two time-scale model based nonlinear control method for a helicopter is proposed. According to the characteristics of the helicopter that different state is with different settling time, the helicopter model is divided into the fast model and the slow model. The backstepping control method and the inverse dynamic control method are separately used to design the controllers for the fast and the slow model. And different control intervals are used for different models. Simulation results show that good performances are achieved by the proposed controller for step and sine change velocity tracking.