Abstract: To reveal the temperature change caused by friction between the wall of coring tube and coal seam during coring process, and to study the gas diffusion law of coal core during real coring process, the temperature field test of the wall of coring tube during coring process and the simulation test of gas diffusion law during coring tube under different conditions are carried out in this paper. The results show that the temperature changes in coring process are mainly divided into slow heating stage, fast heating stage and slow cooling stage. Three groups of simulation tests were set up for simulating the gas diffusion law in the core of the coring tube: under the same gas pressure, the desorption amount of gas in the core is less than that in the coring process at the constant ambient temperature; under the same gas pressure and the heating rate of the tube wall, the greater the coring depth, the greater the desorption amount of gas in the core. The main factor affecting the gas loss is time. Under the same core gas pressure and core depth, the gas desorption capacity increases with the increase of wall temperature rising rate. In the field measurement of gas content in coal seam, the temperature of coal core should be lowered as much as possible and the coring time should be reduced, so as to restrain the loss of gas content and improve the accuracy of gas content determination.