Abstract: The mine-used frequency converter is connected with motor through a long cable, and there is phenomenon of voltage reflection in transmission process of pulse width modulation(PWM) pulse, which causes spike voltage at the motor end and seriously affects operation reliability of frequency conversion driving system. At present, mine-used flame-proof frequency converter usually adopts series output reactor to suppress spike voltage, but suppression effect is limited. And the methods of suppressing spike voltage by using RC filter device and LRC filter device mainly aim at 380 V and 660 V frequency converter, which cannot meet requirement of suppressing spike voltage by 1 140 V frequency converter in underground coal mine. In view of the spike phenomenon caused by long-distance transmission of long cable, the effects of motor load, PWM rising time and cable length on the spike voltage in practical application were analyzed. The reflection coefficient of long cable terminal is not sensitive to change of motor load, and influence of motor load can be ignored in design process of filter parameters. The longer the rising time of PWM and the shorter the cable length, the smaller the spike voltage at the end of the motor.According to the above analysis, combined with cable length and device power loss, a design scheme of LRC filter device suitable for 1 140 V frequency converter in underground coal mine was proposed. Before PWM pulse signal is introduced into the long cable, the LRC filter device is used to delay PWM rising time, so as to achieve the purpose of suppressing spike voltage and high du/dt. Simulation and experimental results verify effectiveness of the filter device.