Abstract: Aiming at big mining deep coal mine threatened by high pressure water, the working face need to grouting reconstruction before mining, and the design of drilling generally uniform holes in the face of upper, middle and lower part, this way of designing the drilling has a large workload, low efficiency of faults. Through 3D electrical method for working face detection, delineating the rich water area, analysis the main fracture direction, determine the target area, to focus on grouting target area. When grouting is completed，the effort of grouting requires again to detect by the 3D electrical method ,the weak of grouting need to reinforce the floor, In order to meet safety requirements for mining. Tanking the mine caozhuang’ s face of 101002 threatened by water for example, through 3D electrical method for the face detection and grouting test，the working face was safety mining, the floor didn’t inrush water，this technology has a strong practicability and popularization.

Key words: 3D electrical method, the floor of grouting, pole-pole device, the technology of slice