The activation of crowbar protection and its resistance value will alter the reactive power dynamic characteristics of Doubly Fed Induction Generator (DFIG) during the Low Voltage Ride Through (LVRT) period, which will affect the wind farm district grid voltage stability. To solve this problem, the influence mechanism of the crowbar protection on DFIG reactive characteristics and its variation law under different grid voltage sags and low voltage transition periods are analyzed in detail. Then, a novel crowbar protection scheme based on dynamic resistance for reactive power improvement of DFIG is proposed. And the corresponding crowbar resistance setting method and switching control strategy are established. Finally, the comparative studies are carried out. Simulation results show that compared with the traditional crowbar protection for current limitation and the active crowbar protection for generator controllability recovery, the proposed crowbar protection scheme can shorten the activation time of the crowbar, reduce the reactive power absorbing, and improve the terminal voltage of the DFIG during the fault. It can also minimize the oscillation peak values of the reactive power, and consequently accelerate the grid voltage recovery after clearing the fault, which is helpful for enhancement of the system district voltage stability. This work is supported by National Natural Science Foundation of China (No. 51577096 and No. 51761135015).