Abstract: According to the left coal spontaneous combustion problem of the goaf in a small coal mine in No.4 seam at the east part of Maying Mine, an isotope rad on measuring method was applied to the firing zone detection of the goaf.There were 13 firing zones detected in total with the total area of 27 513 m2 and the position and development tendency of the firing zones were determined.The detected results and the previous general investigated results were quite fitted.Thus the feasibility 0 f the radon measuring method applied to the regional detection of the firing zones in the eastern minefield of Maying Mine was confirmed.The detection results of the is otope radon measuring method could provide technical basis to make the technical control plan and measures of the firing zone in the goaf of the small mine.