Abstract: In order to further study the deformation characteristics of interaction between coal and gas, a dynamic test system of adsorption deformation for coal sample under triaxial stress was developed to measure the adsorption capacity and adsorption deformation of carbon dioxide and methane in soft coal and hard coal of the dynamic test under triaxial stress, and established the deformation model of gas adsorbed by coal under triaxial stress. The results show that: ① The adsorption curves of soft coal and hard coal to carbon dioxide and methane gas under triaxial stress condition meet with the Langmuir equation.The adsorption capacity of soft coal is larger than hard coal under triaxial stress condition, and the amount of methane adsorbed by both coal samples is less than that of carbon dioxide. ② Under the condition of constant stress, the deformation of soft coal adsorbed gas is greater than that of hard coal adsorbed gas. ③ The dynamic evolution process of adsorption deformation for soft coal and hard coal under triaxial stress can be divided into three stages: initial rapid deformation stage, slow deformation development stage and deformation stability stage. ④ The deformation of coal samples increases with the increase of adsorption capacity under triaxial stress.