Abstract: In order to study gas permeability features of No. 5 and 7 seams in- 850 m level of Qianjaying Mine,type MZY- I coal seam permeability measuring meter was applied to measure gas permeability law of seam under the conditions of different gas pressure. The experiment results showed that under the condition of same temp erature and surrounding pressure,gas permeability rate would be lower with gas pressure increased in coal mass and gas permeability would be reduced lower with gas pr essure increased. Based on occurrence conditions of No. 5 and 7 seams,geostress measured was 19 MPa and gas pressures were 0.89 MPa and 0. 58 MPa individually. As the tests conducted in No. 5 and 7 seams,under gas pressures of 0. 89 MPa and 0. 58 MPa,seam permeability coefficients λ were 0. 854 4 and 0. 6478 m2/( MPa2.d) in dividually and seams were both difficult gas drainage seams. The study conclusion could provide reference to study on gas dynamic disaster prevention and control theory of coalbed methane mining technology in- 850 m level of Qianjiaying Mine.