Abstract: The basis of safe and efficient mining of pitching oblique mining area of steeply dipping seam is the stability control of “support-surrounding rock”JP system. Affected by the uneven filling of gangue and dip angle, the stability control of “support-surrounding rock” system is difficult. Taking No.3132 working face of a mine as the research background, using the method of physical similarity simulation experiment and theoretical analysis, the space-time evolution law of collapse gangue filling in pseudo downdip stope of large dip coal seam and the interaction relationship of “support-surrounding rock” system under the action are studied, and the support mechanical model is established, The effects of pseudo slope angle of working face and gangue force on the critical resistance of support are determined. The results show that the sliding filling of gangue in pitching oblique mining area goes through three stages: preliminary filling of lower area - gangue inclined sliding-filling of depression area; The length of roof connecting area of goaf filling body increases with the increase of coal seam inclination, direct roof thickness and working face length, and the length of free area increases with the increase of coal seam inclination, mining height and working face length. The asymmetric accumulation form of gangue changes the stress conditions and fracture characteristics of roof, and the load of support presents obvious asymmetric and regional characteristics; The collapse gangue in the pseudo downward inclined stope frequently has an impact and contact effect on the tail of the support. The critical resistance of the support increases with the increase of the gangue force and decreases with the increase of the pseudo inclined angle of the working face. The support in the middle and lower areas of the working face needs greater support resistance than the support in the upper area to resist the influence of the gangue. The field monitoring results of the working face verify the rationality of the theoretical model.