In this paper. we consider impulsive control of a periodically Forced pendulum system which has rich chaos and bifurcation phenomena. A new impulsive control method for chaos suppression of this pendulum system is developed, Some simple sufficient renditions for driving the chaotic state to its zero equilibrium are presented, and some criteria Fur eventually exponentially asymptotical stability are established. This work provides a rigorous theoretical analysis to support some early experimental observations on controlling chaos in the periodically forced pendulum system.