Abstract: According to the floor water inrush of 911 mining area during initial mining stage of the first strip working face in Bucun mine,the influence of working face width on the depth of floor failure is studied by the method of numerical simulation and field measurement.The results show that when strip width is 15~20 m,the corresponding depth of floor failure is 5~7 m;while the effect of more faces is superimposed the maximum depth of floor failure is 10 m.The resource recovery is improved through increasing working face width from 15 m to 20 m,while prominent economic benefits is obtained under the condition of safety mining.