Abstract: This paper constructs a risk assessment system based on 23 indicators from 3 aspects of occupational health, safety and environment to scientifically evaluate the risk of one-ventilation and three-prevention system in coal mine. On the basis of work breakdown structure and risk breakdown structure （ＷＢＳ－ＲＢＳ） and analytic hierarchy process （ＡＨＰ）, a risk evaluation model is established. The evaluation model is applied to the risk assessment of one-ventilation and three-prevention system of a mine in Guizhou, the system risk level has been derived. The evaluation results objectively reflect the risk situation of the coal mine. The calculation is simple and the results are accurate and reliable.