Abstract: The water sand filling method was used in the early stage of a subsequent filling mine,and the water secretion effect of the filling body was poor,and the filling body was rich in water. With the increase of water-sand filling area,the stability of roof and hanging wall of the stope becomes worse. In order to improve the mining safety,the mining enterprise adopt the cemented filling method. Therefore,it is urgent to set isolated pillar between water sand filling body and cemented filling body to ensure the safety of subsequent mining activities. In this study,the theoretical analysis model of side wall pressure inclined pillar is constructed,and the hydrostatic pressure gradient of 10~ 15 m width water sand-cemented filling isolated pillar and different water sand filling bodies is studied by FLAC 3D numerical simulation software. The study results show that:① Mining disturbance will cause stress concentration in the isolated pillar,and the non-solidified water sand filling body will further increase the maximum principal stress in the pillar. ② The redistribution of the stress of the pillar and the horizontal pressure of the water sand filling body increases the horizontal displacement of the pillar,and gradually produce damage and form a plastic zone. The 10~ 13 m isolated pillar is not enough to support the stability of the stope under the water bearing condition of the filling body. ③ Considering the influence of blasting disturbance,in the case of existing water rich backfill,the recommended isolated pillar width is 15 m. ④ When the width of isolated pillar is 15 m,with the increase of hydrostatic pressure gradient,the maximum principal stress and displacement in the pillar increase slightly,and the plastic zone does not increase significantly,indicating that the 15 m isolated pillar can ensure the safety of the stope in the mining process.