Abstract: In this paper, the output tracking of the nonlinear system with nonlinear parameterization is considered. Using the time-varying state feedback control law exponentially stabilizes the output tracking error, and guarantees that all states in the nonlinear system are bounded. To implement the time-varying state feedback control law, design the high-gain robust observer which observes the states needed by the control law. The output of the obtained closed-loop system can asymptotically track the desired output, and all signals inside the closed-loop system are bounded.