Inhibitors can improve the moisture absorption and moisture retention, physical oxygen barrier capacity of coal, and reduce the active groups on the coal surface, which technology is an effective fire extinguishing technology in coal mines. The application processes of inhibitors includ surface spraying of coal residues, drilling and pressure injection of coal seams, etc., but the difference in inhibitory effect corresponding to different application processes has not yet been grasped. Guotun coal samples were adopt with MgCl2 as the inhibitor solution at a mass concentration of 20%. The inhibitors were sprayed onto the coal surface and the coal samples were immersed in the inhibitor solution to prepare sprayed inhibitor samples and inject resistance coal samples. The temperature-programmed test shows that during the low-temperature oxidation process, the oxygen consumption rate, CO production and cross-point temperature of the pressure-inhibited coal sample are always the lowest. The inhibition rate of pressure-injected inhibited coal samples is significantly higher than that of sprayed inhibited coal samples. When MgCl2 is used as the inhibitor in coal mines, from the perspective of fire extinguishing effect, it is recommended to give priority to the construction process of drilling and injecting inhibitor into the coal seam.