Abstract: The motion equations of an elliptical pendulum system under periodic perturbation are derived by using the generalized Lagrange equation. The equations are solved numerically to investigate the process of the deformation,distortion,split of the invariant torus and the chaos. Moreover,the influences of the perturbation frequency and the mass parameter on the chaotic behavior are discussed through analyzing the maximum Lyapunov exponent.

Key words: periodic perturbation, elliptical pendulum, chaotic behavior