Abstract: In this study, we illustrate the nonlinear oscillator with a discontinuous term which is arising from the motion of rigid rod on the circular surface without slipping. At first we explain the problem. Two powerful methods, Parameter Expansion Method (PEM) and Variational Iteration Method (VIM), which has good accuracy and efficiency applied to solution. The results compared with the forth order Runge-Kutta. The advantages of using these methods are high accuracy and simple procedure in comparison to exact solution.