Abstract: In view of the current situation that the application conditions of hydraulic pressure relief and permeability enhancement technology are not clear and the effect evaluation index is unknown, by analyzing the technical principle of hydraulic measures, the applicable conditions and evaluation indexes are preliminarily determined: hydraulic flushing, hydraulic slotting and hydraulic fracturing are respectively applicable to soft coal seams with the coal solid coefficient f < 0.5, medium and hard coal seam with the coal solid coefficient f > 0.5, and medium hard coal seam with the coal solid coefficient f less than 1 and more than 0.5; the rate of discharge cuttings, coal output from drilling and pressure relief deformation, rate of water content or increment of coal seam are used as evaluation indexes respectively.