Systematic investigations were conducted on the rock samples collected from the Ruqigou coalfield in Ningxia.As the rock temperatures vary with the combustion degree,the authors made a serial of calefaction experiments on the rock samples.The results demonstrate that the rock magnetism varies with temperature.The feasibility of applying the magnetic method to detecting the underground coal fires was studied and,in addition,the human-computer interactive inversion algorithm was used to process the measured data.The inversion result fits the measured data well and can determine the combustion center and delineate the coal fire area effectively.