Based on pressure relief and permeability increase technology used by highpressure water jet slottingresearched the changes of slotted coal seam permeability.Analyzed the effect of stress and pressure on gas permeability of coal.According to the actual slotted process to set modelusing FLAC simulation softwaresimulated the change characteristics of the relief effect scope of slotted coal.Adopted a similar method of physical modeling experiments and established similar model to measure permeability variation when the process of slotted coal seam pressure relief changesand conducted field trials.The results show that the pressure relief around coal after slottingcoal permeability increases with the impact of pressure relief after slotting.Field test results show that after slottingcoal seam permeability increases to 113 times of the originaleffective influence on extraction expands to 2 times of the original radius.