Abstract: In order to realize safe mining under the water of 1706^-1 working face in Duolunxiexin Coal Mine,the collapse-production ratio and crack-production ratio of working face were determined by "two zones" height empirical formula expectation, "two zones" height measurement, similar simulation test and FLAC^3D numerical simulation. Based on the coal pillar design security requirements and bedrock, the safety mining thickness of working was calculated. The results showed that "two zones" height estimation of working face overburden rock failure was more reasonable by the measured values of collapse production ratio 5.61 and crack production ratio 12.21. The working face safety mining thickness could be divided into two pieces, including the thickness 8.9 m which was from cut open to the boundary area and 4.7 m which was 480 m away from the stopping line "bottom gravel area". The maximum water estimation amount of 1706^-1 working face was 27.75 m³/h, normal water amount was 25.66 m³/h which was far more less than the normal water amount of coal mine water drainage device. Therefore, it would not cause coal mine flooded accidents, the normal mining could be carried out in working face.