A design method of the wind farm automatic voltage control（AVC）system considering the doubly-fed induction generator（DFIG）as reactive power resource is proposed.And its control performance is validated through field tests.This paper focuses on issues in wind farm AVC engineering，such as DFIG reactive power capacity assessment，equipment control circle matching，control dead zone setting，to solve problems of low credible reactive power capacities，poor voltage controls and quick fluctuation of control objects，respectively.Simplified strategies based on power flow sensitivity control are also studied.Field tests prove that the corresponding settings and simplification strategies work well and the AVC system can improve the voltage notably.