In order to realize the effective detection and localization of the unexploded ordnance, an electromagnetic detection system with small transmitting coil and array receiving coils has been developed. The primary field interference is removed by using the eccentric configuration between the transmitting coil and array receiving coils. Because of the array receiving coils, the detection efficiency of the system is effectively improved. The horizontal location algorithm based on differential comparison of the response of array receiving coils is proposed, and the feasibility is verified by experiments. The research results show that the detection depth of the detection system for the typical annular metal cylinder reaches 1 m, and the location error between the calculated value and the actual value is 3. 76 cm. The system and method are able to realize the accurate detection and location of the unexploded ordnance.