Abstract: In order to study the magnetic variation of coal and surrounding rock in the post-combustion fire area, and provide the basis for the magnetic method to detect coal field fire area, the rock, gangue and weakly caking coal in Huangling Mining Area were selected as the samples which are heated from room temperature to 600 ℃ in the gradient, When they are cooled to normal temperature, the specific magnetization rate of the samples under different magnetic intensity are measured. The results show that the higher the temperature, the higher the specific magnetization of coal and rock; compared with the rock and coal gangue, the specific magnetization rate of coal is more obvious affected by temperature, and coal is diamagnetic, which is not affected by the strength of external magnetic field when the temperature is at 25 ℃ to 200 ℃; the magnetic susceptibility of coal increases rapidly at temperature of 200 ℃ to 400 ℃, coal susceptibility increased slowly after 500 ℃; furthermore, the specific magnetization rate of coal after high temperature treatment decreases with the increase of magnetic field intensity just as rock and coal gangue.