Abstract: For researching grouting diffusion process and it's mechanics mechanism, we conducted grouting experiments by high pressure seal grouting experiment system, and know the grouting diffusion process including channel seepage and pore penetration. We analyzed slurry pressure change in finger-shaped channel during percolation process, and obtained the results that slurry pressure loss is increased with the increasing of slurry viscosity and channel length and grouting quantity, and reduced with the increasing of channel diameter; we derived diffusion radius relationship of pore penetration in the vicinity finger-shaped channel, and proposed the measures for improving grouting effect, and get good results in the grouting project when the fully mechanized caving face passed through wind oxidation zone in Pingshuo Coal Industry Company No.1 Coal Mine.