The working status of huge rotating mechanical equipment can be judged with the method of detection and processing its acoustics. It is analyzed that the variation of the sound reflected the variation of the material percentage in the equipment. The sound caused by different material percentage is collected and analyzed in time and frequency domain in this paper. A practical material percentage detection algorithm is proposed. The frequency spectrum of quantitative analysis for the material percentage is determined. The procedure of algorithm design includes calibration and quantitative detection. The field detection results show its effectiveness.