Abstract: Accurate prediction of the maximum failure depth of the stope floor on confined water is an important part of preventing water inrush from the coal mine floor. In order to study the failure characteristics of the inclined floor along the working face, the author based on the mine pressure and rock strata control theory, considered the combined action of the inclined bearing pressure of the stope floor, established a mechanical calculation model for the inclined floor of the stope above the confined water, and used the Mohr Coulomb yield criterion with tensile failure to judge the failure of the stope floor. The results show that: under periodic pressure, the failure pattern of the stope floor along the dip of working face tends to be similar to an “inverted saddle shape”, and the maximum failure depth is 12 m; the floor failure depth on both sides of the working face is greater, and the failure depth of the gob floor is small. Numerical simulation calculation results show that the maximum failure depth of the floor near the elastoplastic boundary of the working face is 13 m, and the failure mode is mainly shear failure. Located in the pressure relief section of the gob, the failure depth of the stope floor is small, and the main failure forms are shear failure and tensile failure. This is almost consistent with the failure mode of the stope floor on confined water obtained through theoretical analysis. The maximum failure depth of the floor of 22516 working face in Dongjiahe Coal Mine is 13.52 m, which is relatively close to the 12 m calculated by the author through theoretical analysis and 13 m calculated by numerical simulation. The rationality of the author's theoretical model establishment and the correctness of the numerical simulation analysis are verified. The research method provides a new reference for analyzing the failure characteristics of the confined water stope floor.