Aiming at the problem of insufficient measurement accuracy caused by eccentricity of tunneling magnetoresistance (TMR) current transducer in direct current (DC) measurement of distribution networks. A symmetric four-air-gap current transducer based on TMR is proposed in this paper. Numerical simulation models for single-air-gap, symmetrical dual-air-gap, and symmetrical four-air-gap TMR current transducers are established using the PSCAD simulation platform. The DC step response and alternating current (AC) frequency response are simulated and analyzed. The simulation results demonstrate that the magnitude errors of the symmetrical four-air-gap TMR current transducer in measuring the DC step response are reduced by 89.04% and 0% compared to the single-air-gap and symmetrical dual-air-gap TMR current transducers, respectively. Additionally, the amplitude errors in measuring the 50 Hz AC frequency response are reduced by 40.13% and 37.74%, respectively. The correctness of the numerical simulation model established in this study is verified. Eventually, the TMR current transducers are applied in the DC power grid test system proposed by the International Council on Large Electric Systems (CIGRE). The results demonstrate superior measurement performance under both normal operation and fault conditions.