Abstract: In order to analyze the distribution and variation law of transient electromagnetic field intuitively, the response equations of transient electromagnetic field under different damping states are theoretically derived, including a modeled transient process of transient electromagnetic field via Simulink. The equivalent circuit modules of excitation current, transmitting loop, geological anomaly body, receiving coil and their mutual inductance modules are developed. The influence of inductance, distributed capacitance and resistance on the equivalent circuit of transmitting and receiving loops are systematically studied. The results indicate a direct determination of the excitation waveform characteristics of the transient electromagnetic field based on the damping state of the transmitting loop, while the damping state of the receiving loop directly affects the attenuation characteristics and the observation quality of the transient electromagnetic field. The circuit simulation results are hugely significant in terms of restraining the non-geological influential factors and guide the design of transient electromagnetic observation system.