When the power grid fault occurs, the current waveform usually experiences mutations or contains a large number of high-order harmonics. In order to obtain and analyze the primary current of the power grid more accurately, this paper models the primary sensing part of the DC electronic current transformer (DC ECT) in a wide frequency domain. This model consists of two parts: a Rogowski coil and a shunt. The Rogowski coil refers to the distributed parameter model, and the shunt mainly considers the influence of inductance components and skin effects. A corresponding broadband simulation model is built in Matlab / Simulink software. Meanwhile, in order to verify the correctness of the simulation model, a testing system for the Rogowski coil and shunt is built on site, and on-site testing is conducted. The actual test data is compared with the simulation data. The results show that the broadband models of the Rogowski coil and shunt constructed can accurately reflect the actual situation. The Rogowski coil can adopt the idea of using multiple segments instead of infinite segments according to frequency and error requirements. The residual inductance and skin effect in the shunt are the main factors affecting its high-frequency characteristics. This paper provides a reference for the study of broadband characteristics of DC ECT.