In order to realize the real-time monitoring, measurement, analysis and comprehensive evaluation of the power quality of underground electrical equipment in coal mine,this paper proposed an explosion-proof underground power quality monitoring system based on current and voltage sensing system,developed the isolated current/voltage sensing unit, high-precision ADC unit and system control hardware system, carried out the electrical explosion-proof design, and constructed the on-line monitoring platform of mining power quality.According to tested to underground 6 kV mining mobile substation, this monitoring system can realize the effective on-line monitoring of harmonic voltage, current and power , and generate monitoring data statistical graphics and statistical curves,accurately reflect the operation level of coal mine underground power grid and provide basis for managers' investment decision-making.