Abstract: Abstract：In order to explore the risk of water inrush from the bottom of the two-level main mining 2nd coal seam in the deep extension of the suburban coal mine, according to the characteristics of the two horizontal floor strata and fault structure in the mining area, the fault structure complexity of the two horizontal floor is adopted by the water inrush coefficient method and the fractal dimension method. The risk of water inrush was quantified and integrated. The results show that although the calculation process and the quantitative partitioning parameters of the two methods are different, the quantitative partitioning performed has good consistency, and the fractal dimension of the fracture structure has a significant positive correlation with the water inrush coefficient value, and the fault structure is complex. The value of the water inrush coefficient corresponding to the area is obviously too large. The comprehensive comparison shows that the water level of the two horizontal coal seams is larger in the east and west, and the middle area is safer. The research results have important reference value for the safety belt pressure mining of the second level and the second coal seam in Chengjiao Coal Mine.