Abstract: The development of coalbed methane shows that fracture and permeability of coal bed are two key factors on the success development of China's CBM resource.The paper systematically studied the change law of fracture width and permeability as stress varied in laboratory experiments.The results showed that fracture width and permeability continuously decreased in the process of increasing effective stress;fracture width and permeability changed very slowly when stress reached to 8 MPa.Thus,fracture and permeability of coal bed are very sensitive to stress.Results showed that coal bed had strong stress-sensitivity.