A nonlinear control is proposed for trajectory track-ing of a 6-DOF model-scaled helicopter with constraints on main rotor thrust and fuselage attitude. In the procedure of con-trol design, the mathematical model of helicopter is simplified into three subsystems: altitude subsystem, longitudinal-lateral subsystem and attitude subsystem. The proposed control is developed by combining the sub-controls for the correspond-ing subsystems. The sub-controls for altitude subsystem and longitudinal-lateral subsystem are designed with hyperbolic tan-gent functions to satisfy the constraints; the sub-control for attitude subsystem is based on backstepping technique such that fuselage attitude tracks the virtual control for longitudinal-lateral subsystem. It is proved theoretically that tracking errors are ultimately bounded, and control constraints are satisfied. Performances of the proposed controller are demonstrated by simulation results.