Abstract: In order to optimize the risk assessment of water inrush from coal floor collapse column, based on the analysis of main influencing factors, the risk assessment system of water inrush from coal floor karst collapse column is established. The optimum weight is determined by using the difference method and the optimum combination analytic hierarchy process （ＡＨＰ） and the principal component analysis method. Finally, the collapse column of Geting Coal Mine was taken as an example for engineering verification, the results showed that the water pressure of aquifer and the thickness of water-resisting layer have the greatest influence on the water inrush of underground collapse column of coal seam. This model can optimize the weight of subjective and objective evaluation, reduce the artificial influence of subjective evaluation method and relying too much on objective data of the objective evaluation. It can reflect the differences among the influencing factors reasonably and objectively and realize the risk evaluation of water inrush from karst collapse column of coal seam floor.