Given that CO2emission rights cannot be effectively arranged relying on market mechanisms alone， differential game theory is used to study the regulation of CO2emission in an oligopolistic electricity market. A Stackelberg differential game model for multilateral competition is proposed. The model can be solved using backward induction and Hamilton-Jacobi-Bellman equation to obtain the optimal government carbon tax and CO2emission allowance price， as well as equilibrium sell price and the optimal distribution ratio of emission rights among generation enterprises in the decentralized decision. Meanwhile， the main economic implications of equilibrium solutions are analyzed and the corresponding decision-making revelations are briefly discussed. Using a six-generator electricity market as an example， the simulation results indicate that the differential game equilibrium is the Pareto improvement of the cases when government makes optimal control unilaterally without considering generation enterprises rational responses.