The dynamic model of Cournot game with bounded rationality in power market is established. The different dynamic behaviors are analyzed, such as Nash equilibrium, period and chaos. The economic performances of dynamic behaviors are analyzed and compared for duopoly dynamic Cournot game. For the chaotic market status which has lower economic efficiency, the parameter perturbation control method is proposed. Finally, by means of the proposed control method, the chaotic state is controlled to the stable equilibrium point so that the economic performance of power market is effectively improved.