Abstract: In this paper,EH-4electromagnetic imaging system is applied to search groundwater-rich area in Nantong coal mining subsidence,conclusions list as follows:Layer T₁f^6-7 in section No.Ⅲis barely influenced by underground mining.NO.Ⅳabnormal section,located in stretched area,is detected as watersufficient area.Groundwater-rich region detected by the EH-4electromagnetic imaging system fits in with the actual subsidence position,which proves EH-4electromagnetic sounding measurement techniques to be effective methods to search groundwater in karst coal mining subsidence.