Abstract: In view of the problem of water and sand inrush accidents during the mining of different coal thicknesses in weakly cemented Paleogene sandy conglomerate aquifers, the mining process of a No.21-1 coal seam in a western mine was taken as the research background, and the thickness of the safe coal seam was determined by the study in order to reduce the possibility of water and sand inrush accidents in the working face.The discrete-element particle flow PFC3D software is used to construct a three-dimensional model of the working surface.Based on the macro parameters measured in the field, the macro-micro parameter conversion formula are converted into the micro-parameters and imported into the three-dimensional model.The simulated thickness of the face is 2, 4 , 6, 8 m at the time of water and sand mixture flow, so as to analyze the possibility of water and sand inrush accidents on the working face.The results show that:from the perspective of the development process of the water and sand inrush channels and the change of the water pressure in the aquifer, when the coal seam mining thickness is 2 m and 4 m, the water and sand inrush channels do not reach the working surface, and there is still a certain amount of water pressure in the aquifer.At this time, the probability of water and sand inrush accidents is small.When the thickness of the coal seam is 6 m and 8 m, vertical cracks appear between the working face and the sand layer are penetrated, water and sand inrush channels are formed and the water pressure of the aquifer gradually decreases to zero in the final mining stage.Therefore, there is a high probability of occurrence of disasters such as water and sand inrush in the working face.The research provides theoretical support for the selection of coal seam thickness and the prevention of water and sand inrush hazards in similar mine working faces.