Abstract: To solve the hidden danger of water hazard in working face and preliminarily detect the influence range of hydraulic fracturing, after the formation of working face, high-pressure water injection is carried out by using boreholes in normal coal seam area to promote the continuous development of pores and cracks in coal seam. At the same time, the water-rich area of working face is simulated. Based on the significant physical difference between the flow and diffusion of high-pressure water and the water-rich area, mining is carried out. The high density resistivity method, transient electromagnetic method and high frequency electromagnetic wave CT were used to carry out joint detection test before and after water injection in this area. The comprehensive geophysical prospecting results were compared and analyzed. Detection test results show that apparent resistivity and attenuation coefficient of coal seam near water injection point change obviously before and after water injection. The apparent resistivity decreases 2~4 times in the range of diffusion radius of about 30 m, and the attenuation coefficient increases about 20% in the range of diffusion radius of about 10 m.