The negative interaction between AC and DC voltage controls of static synchronous compensator（STATCOM）has attracted so much attention that new control models and strategies just have to be developed.The functions and relations of AC and DC voltage controls are described first and the mathematical model of a single machine infinite bus system with STATCOM is established.Then a new cooperative control scheme of STATCOM based on the differential game theory is proposed to solve the negative interaction between AC and DC voltage controls.The effectiveness of the new control models and algorithms are validated by simulations with MATLAB/Simulink，and the advantages of the proposed cooperative control over other control methods have been proved by the simulation results.