When there is unbalanced AC voltage in Wind farm with voltage source converter-high voltage direct current (VSC-HVDC) integration system, the output power to the grid will fluctuate with twice of the grid frequency, and the grid voltage and current waveforms, even more, will be distorted, hence the power quality of the wind farm provided will deteriorate badly. To improve the performances of wind farm VSC-HVDC system under unbalanced AC voltage, a doubly-fed wind farm VSC-HVDC system with unbalanced AC condition is discussed in this paper. Based on the positive and negative sequence double dq decoupling shafting, and taking into account the influence of equivalent impedance of the relevant reactor and transformer, the unbalanced mathematical model of the wind farm VSC-HVDC system is established. Moreover, an improved control strategy is realized with the construction of the positive and negative sequence current setting. Finally, a DFIG wind farm VSC-HVDC system is implemented on the Matlab/Simulink, comparisons of the simulation results with and without the proposed control strategy show that the proposed improved control strategy can effectively suppress the fluctuation of output power and improve the waveform of grid voltage and current.