When there is a large disturbance in the power grid and the voltage drops, the doubly-fed wind induction generator (DFIG) needs to cooperate with hardware modification measures to achieve low voltage ride-through (LVRT). To solve the problem of resistance value setting in the LVRT strategy of a DFIG using stator side series impedance, this paper first derives the expression of rotor transient current and open-circuit electromotive force of a doubly-fed fan, then analyzes the active and reactive power coupling characteristics of the inverter with the operating limit of the inverter during the fault period. Finally, combined with the analysis above, it proposes a resistance optimization method based on the optimal reactive power stator side string impedance. The impedance selection range is determined by the transient current constraint and the open-circuit electromotive force constraint of the rotor, and the impedance value of series connection is optimized with the maximum reactive power output during the transient period as the goal. The simulation results show that the impedance value optimized by the proposed method can not only effectively suppress the transient shock to the DFIG, but also ensures that the unit can provide reactive power during the fault period, support the grid voltage, and improve fault operation ability.