In order to study the influence of reinforcement depth on the deformation and failure of floor rock for the grouting design, the influence of reinforcement depth on the deformation and failure of floor rock under the condition of near Ordovician limestone confined aquifer and thin aquiclude is studied. According to the geological conditions of the mine, the basic shape of the floor rock under the influence of the weathering zone under the mining action is constructed, and the effect of grouting reinforcement on different strata is analyzed. Then, the numerical model is established for verification. The calculation results show that there are obvious mutation points in the displacement curve of the monitoring points when the top layer of Ordovician limestone is weathered. The displacement curve of the monitoring points is divided into three sections, corresponding to the weathered rock, Ordovician limestone and the upper floor rock of the weathered layer. The maximum displacement of the monitoring point with the reinforcement depth of 14 m is less than the maximum displacement of the rock mass without reinforcement, and the displacement decreases by 6.2%; when the weathered rock mass on the top of Ordovician limestone is reinforced, the maximum displacement is less than the maximum displacement with the reinforcement depth of 14m, and the displacement decreases obviously. The displacement curve of monitoring points can be divided into three sections and two sections with mining length of 250 m; with the increase of reinforcement depth, the three sections change to two sections. Grouting reinforcement plays a good role in resisting the deformation of the floor. To a certain extent, the greater the depth of grouting reinforcement, the better the grouting effect.