Abstract: To avoid the water inrush from the floor of the working face, according to the characteristics of large mining height and long working face of 1603 first mining face of 16 coal above Ordovician limestone in Limin Mine, theoretical calculation and numerical simulation method were used to study the distribution of the rupture zone of the 1603 working face. The maximum failure depth range of the floor is calculated by using the statistic empirical formula. The maximum failure depth range of floor calculated by statistical empirical formula is 24.30 to 26.60 m. The maximum failure depth of the floor obtained by numerical simulation is 21.10 m, which is located within the range of 5 m to 10 m in front of the coal wall at the cut hole and below the floor of the working face within the range of 10 m from the coal wall. Compared with the results of theoretical calculation and numerical simulation analysis, the two results are consistent with each other, and based on the results, a safe water-retaining pillar can be reasonably set up.