Abstract: In the process of underground coal mining and gas extraction, coal body will produce deformation effect with gas adsorption and desorption. We analyze the deformation rule of coal body during the cyclic adsorption and desorption of CO₂ gas by using self-designing experimental device that tests deformation of coal during the cyclic adsorption and desorption. Experimental results show that the deformation of coal body under the cyclic adsorption and desorption presents anisotropic characteristics, but that remains the same on the directions of parallel bedding and vertical stratification. With the increase of cycling times, the maximum amount of deformation of each time caused by coal adsorption increases 10%. At the same time of adsorption and desorption, deformation rate of coal on the vertical direction to the bedding plane is faster than that of the parallel direction to the bedding plane. Under 1 MPa pressure, relationship between residual deformation amount of coal and time is linear, that is, ε_rd=kn-a. As the experiment progresses, the damage in the coal structure increases, and the intensity of coal body decreases.