This paper first describes the research background of inverted pendulum, then derives the mathematical model of planar double inverted pendulum system by use of Lagrange modeling method. After partial linearization, we can arrive at the pendulum's equation of state space, which is a controllable, observable, but absolute unstable system after analyzing. Using the pole—placement method, a variable structure controller was designed for the stabilization and robust control of the double inverted pendulum. In order to reduce the chattering of the controller, a new algorithm for the sliding mode control was proposed. Simulation results verify the validity and feasibility of the proposed approach.