Some work has been done for the measurement mode study of TEM with large current and small size central loop: First, the intensity of stimulating field which changes with the depth was calculated, and a comparison was made with fixed loop; Second, the cut-off time was figured out, followed by a comparison with that of the fixed loop; Third, the model was set as the real layers and theoretical prospecting depth was calculated. Then, the data of the test line were also analyzed. It is concluded that TEM with small size central loop could completely satisfy the requirement of conventional prospecting. TEM of small central loop with large current has obvious advantages in theoretical and practical application, such as reduction of shallow layer dead zone and easy construction.