In order to reduce the impact of wind farm grid-connected on power grid and improve the robustness of grid-connected system, a sliding mode variable structure control strategy with feedback precise linearization is adopted to design the control of converter stations on both sides of wind farm grid-connected system via flexible direct current transmission. Firstly,a mathematical model of the voltage source converter in the dq coordinate system is established. Then the sliding mode variable structure control method based on precise linearization decoupling is used to design the converter stations on both sides of flexible HVDC transmission system, which solves the problems of poor regulation ability and difficult parameter tuning of traditional double closed loop control method, and further improves the anti-interference ability and dynamic stability of the state feedback linearization control system. Finally, the simulation model of wind farm grid-connected flexible HVDC system is established in Matlab/Simulink. The simulation waveforms before and after adding sliding mode control are compared to verify the performance of the control system.