Abstract: In order to explore the influence of backfilling mining on the damage depth of floor and the control effect of water inrush disaster, combined with the methods of theoretical calculation, numerical analysis and field observation in coal mine, the failure characteristics of the floor in backfilling mining above confined water in A working face of a mine are comprehensively studied. Theoretical calculation formula for determining maximum damage depth of the floor in backfilling workface is proposed. Through numerical simulation, a comparative study is carried out on the floor failure of backfilling mining and non backfilling mining, and the actual deformation and failure characteristics of floor rock during filling mining are analyzed through field measurement. The results show that surrounding rock stress concentration and roof-to-floor convergence is decreasing because of the existence of the filling body; floor damage depth remain stable, no longer development in the vertical direction with advancing of the workface, mining influence of A workface to the floor is eased for stress transfer function of the filling body, the damage depth of the floor does not reach the limestone aquifer, and the coal seam can be safely mined.