Abstract: Coalbed methane reservoir has a dual porosity system and its permeability is majorly controlled by fracture. The absorption of coal will cause matrix contraction or expansion. So that coalbed methane reservoir is different from conventional oil and gas reservoirs. It is very important that the permeability variation is systematically studied by reservoir deformation. Reservoir deformation is divided into fracture volume compression, matrix compression and matrix contraction/expansion in this paper. The major factors of the reservoir deformation are pointed out. The possibility of deformation and corresponding performance under the conditions are studied by experiment. Based on experimental studies, the mathematical model that reflects the relations between deformation and permeability is established. In this paper, the deformation of coalbed is deeply studied. That is more useful for development and production of coalbed methane.