Abstract: With the vitrinite reflectance measurement, macerals analysis, specific surface area measurement;micro-fracture statistics and methane isothermal adso rption experiments of ten coal and rock samples from nine mining areas in North China, the physical properties of the coal with different metamorphic degree were anal yzed.In combination with the metamorphic background of North China coal, the formation causes of the physical differences were discussed.The study showed the coal metamorphic degree and the metamorphic type would affect to the coal micro structure, the pore structure and fracture evolution law and those would be the main caus es to the physical differences of coal.The micro analysis showed that when coal at different metamorphic stage, its macromolecule structure would have series variation and thus would cause the coal specific surface area and adsorption capacity with a regularly variation.