The low voltage ride-through（LVRT） capability of wind farms has a great impact on the power system stability. A novel technology is proposed to improve the low voltage ride-through capability of wind farms using series dynamic braking resistor（SDBR） which can boost terminal voltage and dissipate active power. A switching scheme of SDBR is introduced based on the dynamic stability margin of speed-voltage. This paper uses a representative wind farm model based on fixed speed wind turbines to study the transient LVRT stability. Both detailed analysis and simulation results show that SDBR can significantly improve the low voltage ride-through performance of wind farms， and the switching scheme of SDBR is simple and effective. The technology can reduce wind farm's dependence on the pitch control systems and alternatives in riding through low voltage fault， and allow retrofit existing wind farms.