The directly driven wind turbine with permanent magnet synchronous generator （D-PMSG） is investigated. Its mathematical model is deduced and chaotic behaviors is demonstrated while its parameters have a certain range of values or under certain working conditions. A sliding mode variable structure method for controlling chaos in D-PMSG is presented, and realized through controlling pitch angle β. In view of the non-linear property and parameter changing characteristic, etc. for wind turbine, and based on the mechanism of the wind turbine, this paper obtained the wind turbines linear model at a certain condition point under some assumptions, and then proposed the sliding model control strategy by taking full use of the SMCs non-sensitivity merit towards the model error and the parameter change as well as exterior disturbance. the simulation result indicates that the proposed control plan is effective, the control property of response is obtained quickly and the system also has good robustness, and is suitable for uncertain parameter in the system. Research results may have value for D-PMSG chaos control.