Abstract: An improved exponential approach method and the system parameter online estimation based on the adaptive theory were implemented in a nonlinear optoelectronic servo system with parameter and structure uncertainties. SMC is applied to the design of APR in the system. Taking the equivalent 1.2sin(0.93t) as the simulation input, the tracking error is less than 60 μrad after 0.45s. The simulation indicates the control method for such uncertain nonlinear system is effective.