This paper describes the basic principles and characteristics of the wider field electromagnetic method and the definition of apparent resistivity of the wider field. Exploration work was carried out in a silver, lead and zinc ore deposit of Inner Mongolia, including the deduction and interpretation of the anomaly. The result compared with CSAMT shows that the wider field electromagnetic method can achieve a larger exploration depth as well as higher exploration efficiency and precision with a smaller distance between transmitting and receiving. Hence the method has obvious effect in search for deep metallic ore deposits.