Abstract: According to the low methane gas production rate ,insufficient study on the coal bed methane mining theoretical law and other problems existed in China coal bed methane development,based on the test comparisons,the adsorption and desorption laws of CO2,CH4 and N2 in coal and rock were analyzed with different te mperatures of 15,20,25 and 30 °C.The test results showed that when the temperature raised,the higher the mean free path of the gas molecules,the smaller the gas ads orption value would be.As for the same medium,when the pressure was the same,the gas with a high critical temperature would have a high adsorption capacity and the CO2,CH4 and N2 adsorption capacity of the seam would reduce in sequence. When the pressure increased,the gas adsorption value of the seam would be increased.Th ere was an desorption hysteresis existed in the pressure releasing and desorption process.When the temperature decreased,the desorption hysteresis would be obviou s which was related to the adsorption and desorption expression and the endothermic reaction.