Abstract: A relationship between permeability of coal-bed and interaction of coal-bed methane and coal was derived according to a capillary model and a singular layer molecular model. Adsorption law of coal-bed methane was obtained by a nonlinear regression method based on experiment data of the adsorption, according to adsorption theories of Langmuir and BET respectively. An example was given and discussed.Results show that the interaction strength is inverse proportion to square root of permeability and pore radius of coal-bed, which suggested the mechanisms why desorption of the methane in low permeability coal is difficult and the methane is not easy to develop, as well as the BET model is better fit for adsorption of coal-bed methane than the Langmuir model. The results can provide coal-bed methane development engineering design with scientific basis.