The AC current in the modern power system will inevitably have a DC component, which causes the AC energy metering error and affects the fair energy measurement. The anti-DC component current transformer can accurately measure the AC current when the DC component exists, but its composite magnetic core is easy to saturate under the condition of large current. This paper uses Ansys Maxwell to model the composite magnetic core of the DC component current transformer and introduces the air gap, and analyzes the influence of the linear range of its operation and the influence of the size of the air gap on the anti-DC component current transformer. The research results show that the air gap helps to improve the linear working range of the composite magnetic core, expand the linear current range during normal operation, and enhance the anti-saturation capability of the transformer.