In order to improve the stability of the power system, power grid requires wind turbines of low voltage ride through capability. To ensure the safety of wind turbines and voltage sag generator during the wind turbines LVRT test, a relay protection system with five relay protection models which includes inverse-time overcurrent protection, instantaneous overcurrent protection, low/over voltage protection, low/over frequency protection and differential protection is designed and verified on LVRT test platform of wind turbines. The results show that the relay protection system can guarantee reliable action in a system failure and no malfunction in low voltage ride through tests. The system can escape the starting peak current of wind turbines, thus protects the voltage sag generator.