In order to cope with the novel power system in a high proportion of new energy grid-connected conditions of current transformer metering range is limited, DC bias magnetization caused by the increase in error, this paper carries out a wide-range, anti-DC bias current transformer key technology research. The research takes the electromagnetic current transformer as the object, through the theoretical analysis of the DC component on the magnetization characteristics of the iron core and the measurement error of the influence mechanism, puts forward a kind of multi-micro air-gap magnetic core structure made of silicon steel sheet and nanocrystalline composite, and based on the air-gap ratio on the remanent magnetism, saturation, permeability and non-linear quantitative relationship to determine the four 0.02 mm micro-air-gap; the flux distribution is simulated using ANSYS Maxwell to verify its stability under 10% DC component perturbation; accordingly, the HL (D)-500/5 prototype is developed, and the IF error test in the range of 0.1%~200% of the rated current and the error test of superimposed 10% DC component are completed in accordance with the accuracy requirement of 0.2SS/2 level. The results show that the proposed composite multi-micro air-gap scheme enables the transformer to satisfy the 0.2SS level with the full-range ratio difference of ≤0.061% and the angular difference of ≤4.3′ under the IF condition; and still maintains the 0.2 level accuracy under the DC disturbance condition, which is significantly superior than that of the traditional structure. The proposed design achieves synergistic optimization of wide dynamic range and DC bias rejection, providing high-precision and highly reliable current measurement technology to support novel power system.