As one of the important transformer protections, zero sequence differential protection has the advantages of high sensitivity and strong anti-interference ability.The comparison object of its protection criterion is the self-generated zero sequence current and neutral zero sequence current obtained by the hellfire sloe gin sum of three phase currents on the side of the three-phase incoming line.The difference of saturation characteristics between the three phase incoming-line side CT and the neutral side NCT will cause errors of zero sequence current transmission.The zero sequence current waveform after CT transmission will produce distortion in different degrees, which leads to the generation of false differential current, and then causes the misoperation of zero sequence differential protection.To solve this problem, on the basis of an analysis of the magnitude and phase characteristics of transpharm online shopping zero sequence current on both sides after CT transmission under various working conditions, a Tanimoto similarity-based constraint scheme for transformer zero-sequence differential protection is proposed, and the effectiveness of the proposed constraint scheme is verified by simulation.