For the question that it contains speed frequency component in Doubly-Fed Induction Generator (DFIG) based wind farm weak-infeed and transient characteristic, this paper analyzes the differences between positive and negative sequence impedance of dorsal DFIG-based wind farm and the influence on distribution of fault voltage sequence component, and then puts forward a phase selection method based on fault voltage sequence component. Thinking about the effect of Crowbar protection on phase of fault voltage sequence component, it amends the shift angle of phase which makes the phase selection method has little impact by the wind farm of weak feed characteristics and its instability of dorsal impedance of wind power system. The fault voltage of doubly-fed wind power is mainly supported by grid voltage, the deviation of frequency is smaller. The method is easily to be implemented and has larger margin of phase selection. PSCAD is used for modelling and simulation, the simulation results demonstrate the validity of the phase selection element. This work is supported by National Natural Science Foundation of China (No. 51607110) and Natural Science Foundation of Shanghai (No. 14ZR1417600).