Abstract: To deeply study the adsorption characteristics of coal body under different pressure conditions and the change of pore structure of coal body, the experimental study on gas adsorption in coal by nuclear magnetic resonance (NMR) technique was carried out. The test results show that: the micropore peak area of the experimental coal sample> the area of the large pore peak> the area of the fracture peak, indicating that the micropores of the coal sample are most developed, and the pore size of the coal body is mainly micropores, and the connectivity between the voids is not strong, gas is not easy to circulate; with the increase of pressure, when the gas pressure reaches a certain level, the coal will generate new pores, and the tiny pores will connect to form micropores or mesopores, and the mesopores will connect with each other to form cracks. It provides the conditions for gas desorption in the next step, and the instantaneous gas desorption occurs; the gas adsorption and desorption characteristics of the coal sample are divided into the ascending phase, the violent phase, the basically constant phase. The gas adsorption capacity increases with the increase of gas pressure generally. Under different gas pressures, the amplitude of nuclear magnetic signal of nuclear magnetic resonance T₂ spectrum changes significantly, and the distribution area of T₂ spectrum increases linearly with gas pressure. That is, the porosity of the coal increases as the gas pressure increases.