Abstract: In order to solve the risk assessment of water inrush in the aquifer of weathered bedrock of coal seam roof in Ningtiaota Coal Mine. Based on the analysis of the development characteristics of the weathered bedrock, according to the geological and hydrogeological data, including the proposed water enrichment evaluation index system of the degree of weathering, including weathering index, aquifer thickness, permeability coefficient, brittle plastic rock thickness ratio, unit water inflow and core take rate, and on this basis of weathering the bedrock aquifer of water abundance evaluation. In order to predict the height of water-conducting zone of the roof more accurately, corrected the empirical formula according to the measured data, and obtained the formula for calculating the height of the water flowing fractured zone which accords with the actual situation of the study area. According to the calculated height of water-conducting zone, the safety of roof cracking is partitioned. Combined with the result of water abundance evaluation, the risk of water inrush from bedrock aquifer of coal seam roof is evaluated.