With the deepening of the study of the transient electromagnetic method, the application of this method has become increasingly extensive since its introduction to China in 1970s. To solve the problem of sustainable development of the Dachang mine, the authors carried out a new round deep prospecting in the periphery of Dachang by adopting high-power TEM. The result is satisfactory in that the inferred mine fits well with the known information. It is concluded that this prospecting method is effective in Dachang, and that the new anomaly targets delineated by high-power TEM is reliable. The successful application of the high-power TEM in Dachang shows that this technique is effective in deep prospecting of metallic deposits.