Abstract: In order to overcome the problem of traditional differential protection being prone to misoperation and insufficient fault recognition sensitivity under excitation inrush current, overexcitation and other working conditions of converter transformers, research on differential protection methods for converter transformers based on magnetic flux characteristics differences is carried out. Extract the current on each side of the converter transformer and calculate the differential current and braking current to obtain the original protection input; Construct a magnetic flux trajectory identification criterion to distinguish between excitation inrush current and internal fault current by utilizing the difference in magnetic flux characteristics between converter transformers and ordinary transformers in saturated and unsaturated states; By integrating the characteristics of magnetic flux differences and adaptive braking coefficients, a segmented differential protection action criterion is constructed to enhance the selectivity and reliability of protection in complex transient processes. The experiment shows that this method can reliably operate in various scenarios, and has stronger anti misoperation ability and higher fault sensitivity compared to traditional schemes.