Abstract: The current harmonic distortion reflecting the maximum load current was defined, and a distortion power factor considering non-sinusoidal current waveform was built according to special requirements of coal mine electrical load. The power quality was represented by several indexes of voltage, current and power factor showing each aspects of electric energy. The minimum mean square error method was used to screen electricity sub-index, so as to establish comprehensive evaluation index system of power quality which was suitable for power supply system of coal mine. By calculating weights of each index using entropy weight method, the comprehensive quantitative evaluation model of power quality was proposed based on probability statistics and fuzzy mathematics. Therefore, sub-index calculation and comprehensive evaluation were achieved. The analyzing results of measured data verify rationality of the constructed comprehensive quantitative evaluation index system of power quality and practicability of the evaluation method.