With the development of AC and DC distribution networks and the increasing number of rectifying loads, this paper presents DC components in the AC grid, which causes the error characteristic of conventional Single-core Current Transformer (SCT) to be extremely poor. Based on the study of SCT misalignment mechanism with DC component, a composite dual-core anti-DC Current Transformer (DCT) comprised of high magnetic permeability core and low permeability core is designed to resist DC component. By the analysis of equivalent circuit and magnetic circuit, its error characteristic and measurement performance are studied. The measurement performance test based on proportional DC superposition method shows that the AC measurement performance of DCT is similar to that of SCT, and its accuracy meets the class of 0.2. For AC current with DC component less than 40%, the measurement performance of DCT is obviously better than that of SCT. The ratio difference of DCT is less than 3%, and the phase difference of DCT is less than 360', which shows DCT has good anti-DC performance. This work is supported by Science and Technology Project of State Grid Corporation of China (No. 52182018000F).