Abstract: In order to study the mechanism and process of mercury migration under the influence of coal spontaneous combustion and coal field fire area, this paper uses the method of combining theory and experiment to study the migration of mercury. In this paper, the transport equation of mercury in porous medium and semi-infinite medium is established from the viewpoint of heat and mass transfer, and the transport equation of mercury in temperature field is deduced. The results of heavy metal content determination of samples from 5 sites including No.12 coal sample before and after combustion by the project team showed that a large amount of mercury migrated from coal after combustion. The project team also measured the mercury content in the surface raw coal of Wuhushan Coal Mine, coal burning and coal from No.12 coal seam. The measurement results verified that a large amount of mercury was released when coal was burned, and summarized the change rule of mercury content in No.12 coal seam. The experimental results show that the abnormal area of high temperature in coal field fire area can be judged by measuring the concentration of gaseous mercury on the surface of coal field fire area.