Abstract: For studying diffusion characteristics of slurry under condition of high stress and high water pressure and high grouting pressure, we developed high pressure sealing grouting experimental system. The experimental system included 5 subsystems which are grouting medium loading system, ground stress loading and regulating system, water pressure loading and regulating system, high pressure grouting system, image collection system. This system can study the relationship between ground stress & water pressure & grouting pressure and diffusion radius of slurry, and can study seepage law of slurry in grouting medium. According to grouting experiment results, we obtained reasonable grouting parameter, and applied the results in caving face pass by wind oxidation zone in Pingshuo Coal Industry Company No.3 Coal Mine, and saved grouting materials cost of 56%.