Abstract: In order to study the floor failure characteristics and depth of deep inclined coal seam floor, taking 8469 working face of Yangdong coal mine as the research object, the stress distribution pattern, plastic zone development and failure depth are analyzed by using the methods of theoretical analysis, numerical simulation and field measurement.Through numerical simulation and theoretical analysis, it can be seen that after the coal seam mining, different stress zones are generated by the supporting pressure acting on the surrounding rock mass and coal seam.Along the strike direction of coal seam, the stress changes symmetrically, whose shape is similar to "saddle", and stress concentration occurs at both ends of the working face; as for dip direction, under the action of inclined stress, the floor mining failure will be transferred to slip failure.The plastic failure zone and stress disturbance are approximately a "spoon shaped", and the maximum stress concentration area appears at the lower side of the working face.With the working face advancing forward, the failure area of the floor increases correspondingly, but the failure depth does not increase after 255 m.Field testing showed that the shallow strata of the floor was disturbed earliest and most affected.The range of disturbance increases with the decrease of the maximum water injection, and the rock strata in the range of 25 m below the bottom plate are less affected.From these methods, it is concluded that the failure depth of the coal seam floor is 25.0-29.2 m.