In this paper, the 8# coal seam coal sample of Malan Mine is selected as the research object, and the triaxial seepage test is carried out. Based on the principle of energy consumption and the definition of damage, the relationship between damage variable and permeability is discussed. The results show that before the unloading pressure, the permeability of coal body decreases with the increase of axial pressure. The energy absorbed by the coal body is mainly converted into elastic energy and stored in the skeleton structure of coal. The permeability of coal body is damaged. The increase in logarithmic function decreases; after unloading the confining pressure, the permeability of the coal begins to increase, and the stored elastic energy is converted into dissipative energy for the destruction of the coal body. The damage increases and the permeability increases with the increase of the damage. The relationship grows, and it is found that the damage variable reaches 0.7 is a key point of coal body damage.