The permeability of coal is an important parameter in the theory of coal reservoir gas flow. Experiments have demonstrated that after the coal matrix adsorbs gas, adsorption swelling deformation will occur and when gas desorbs from coal matrix, it undergoes a shrinkage deformation. A new formula for estimating permeability is developed. By considering the adsorption swelling and desorption shrinkage deformation in this formula for permeability, the effect of coal matrix swelling and shrinkage on coal reservoir permeability is studied. The study shows that, as gas in the coal reservoir desorbs, gas pressure decreases and the coal matrix shrinks, so as to make swelling deformation smaller and increase the permeability of the coal reservoir. In addition, the influence of effective stress, Klinkenberg effects, burial depth and natural fracture on coal reservoir permeability is analyzed. The analysis and research is of significance to coal mine gas disaster prevention and coal bed methane gas resource development.