Abstract: Water in Burnt rock may lead to hidden trouble to safety in production.We detect the burning area in Da Nanhu coal mine using transient electromagnetic technology.Through cross-section and horizontal slices of the apparent resistivity, combining with geological information, we evaluate the water richness of burnt rocks in fire zone, draw the bottom plate contour map of burnt rocks, and delineate the range of burnt rocks.The detection results are basically tallies with the drilling verification.It provides a reliable technical support for safe production of coal mine and hydrologic exploration.