Abstract: Taking the fully mechanized top coal caving mining under water-rich extra-thick sandstone conglomerate in Ili Yining Mining Area as the engineering background, using field measurement, the fracture and mining ratio of overlying rock is 7.5, and the height of water flowing fracture in 2601 working face under different mining height is predicted, and the safety mining height is about 5.0 m. Verification results of solid-liquid coupling simulation show that under the condition of mining height of 8.5 m, water inrush occurs when the working face advances 90 m, and the water pressure of the aquifer before the water inrush has a trend of slow decline, rise, shock and sharp decline; under the condition of mining height of 5.0 m, there is no water inrush in the working face, and the fracture height of the overlying rock is only 37 m, which is similar to that of fracture mining ratio of 7.5, and the fully mechanized height 5.0 m of 2601 working face is feasible.