The invention provides a grounding network imaging method based on a transient electromagnetic method. A transient excitation source detected by the transient electromagnetic method is used for exciting a transmitting coil to generate transient current, the transient current excites out a primary magnetic field, the transmitting coil directionally sends the primary magnetic field to an underground area covering a grounding network, the primary magnetic field propagates underground, the grounding network generates induced current under the excitation of the primary magnetic field, and at the same time, the induced current excites out a secondary magnetic field. In addition to determining the electrical distribution structure and spatial morphology of an underground conductor by using the change relationship between the secondary magnetic field generated by excitation of the primary magnetic field and the time, the induced current of the grounding network generates electromagnetic force under the combined effect of the primary magnetic field and the secondary magnetic field. According to the invention, the excitation source of the transient electromagnetic method is used for exciting a sound field, an ultrasonic receiving array is used for receiving an ultrasonic signal, the received ultrasonic signal data is analyzed, and the structure of the grounding network is reconstructed through the change of the acoustic impedance when the ultrasonic signal propagates in the grounding network. The method provided by the invention can realize high-resolution detection of an ultra-shallow grounding network.