In the process of transient electromagnetic detection, the receiving coil will be disturbed by the primary field, which makes it difficult to accurately extract the secondary field caused by the geological body in the early total field signal. Therefore, the late signal is often used to carry out exploration work. The author intends to design a device and calculation method for extracting early secondary field signals to be applied to shallow exploration.Methods: Based on the conductive ring model, the influence of the primary field on the secondary field signal under different delay conditions was analyzed. According to the magnetic induction distribution characteristics of the transmitting coil in space, the numerical conditions for the cancellation of the primary field are derived.Results: The simulation results show that under the influence of the primary field, the earlier the time is, the greater the difference between the total field and the secondary field response is. Through theoretical calculation, the conversion coefficient of the reference coil relative to the primary field in the receiving coil is obtained, and then the primary field in the receiving coil is offset by the digital compensation method. Automobile experiments show that the pressing rate of the primary field can reach more than 90 %.Conclusions: Compared with the traditional magnetic dipole device, the application of the one-transmitting and dual-receiving device and the secondary field extraction method proposed in this paper can effectively cancel the primary field signal in the total field response, so that the early secondary field signal containing abnormal information can be utilized. It is verified by underground pipeline detection test that the method has a good detection effect in practical work, which is of great significance to improve the ability of shallow geological body anomaly recognition.