A class of single-degree-of-freedom gear dynamic system is considered， and its dynamic equation is expressed as a piecewise linear second-order differential equation. Firstly， the dynamic response is solved by Runge-Kutta method with variable step sizes， and the bifurcation diagram， phase diagram and Lyapunov exponent diagram are obtained. Secondly， the unstable periodic 1， 2， 4 and 6 orbits embedded in chaotic attractors are obtained by shooting method. Finally， the chaotic motion of the system is controlled on to the above orbit based on OGY method. The research shows that the OGY method can successfully control the chaos of the single-degree-of-freedom gear system， and the influence of noise on the chaos control is discussed.