Abstract: In order to study the desorption characteristics of coalbed methane in the middle and high rank coal reservoir,this paper analyzed the characteristics and laws of coal seam gas desorption based on the data of desorption of coal and rock in Hancheng mining area.And discussed the relationship between the characteristics of coal and coal, the degree of metamorphism of coal and rock, the micro component of coal and the classification of coal and rock industry groups.The results show that the desorption rate of coalbed methane in the study area is between 13%~72%,the desorption rate of NO.5 coal is the largest.The desorption of coalbed methane has stage character,and the decrease of desorption rate is mainly caused by the change of gas content in coal reservoirs. The initial desorption rate and its attenuation characteristics are related to the pore structure and connectivity of coal and rock.The influence of the rate of desorption in the area is more complex, which the data is more discrete.But the desorption rate was not significantly correlated with the degree of coal metamorphism, but decreased with the increase of ash yield, and increased significantly with the increase of water content.The increase of the content of vitrinite mirror can increase methane desorption rate, while the content of vitrinite inertinite is on the contrary.The desorption rate of coal No. 5 and No. 11 coal in Xue Feng area , No. 5 coal in South of Wang Feng area and west of Wei Dong area , No. 11 coal in the southern part of Wei Dong area was higher,which is more than 50%,conducive to the development of coal-bed methane.