Abstract: To investigate the process of water inrush related to the underlying collapse column in coal floor and the influence of the height of collapse column, the magnitude of floor strata strength and hydraulic pressure, numerical simulation based on the finite element code was applied to explore the process of the underlying collapse column activation and floor strata fracture initiation, propagation and coalescence. Through observation of the stress field and damage field, water inrush pathways were initially calibrated and the regular results of 3 factors were studied and analyzed in detail. A model was established based on 2171 working face at Fan'gezhuang Mine in Kailuan to figure out the water inrush cause and related influence. Conclusion showed that a collapse column got failed under hydraulic pressure and then ripped into coal floor at the altitude of -390 m forming the water inrush pathway and water disaster.