No matter eomagnetically Induced Current (GIC) which is caused by the solar storms or Ground Electrode Current in HVDC Transmission,besides with the connection of the new nonlinear loads areSresultSin DC component in the grid,which leads to deterioration of error characters of current transformer,would influence the accuracy of the instrument measurement and power measuring.This paper developed the research of anti-saturation performance and error characters of the air gapped core current transformer.A two cores current transformer conbines the air gapped core current transformer and trandition current transformer is put forward on the base of Stheoretical analysis.The mathematical model of the two cores current transformer is established and the error characters are analyzed.TheSeffectiveness of the two cores current transformer are validated by experiment at last.