Abstract: Autotransformers in high-speed railway usually adopt radial split windings. Because the split windings are connected inside the transformer, which is impossible to measure the frequency response analysis（FRA） curves of each split winding outside the transformer directly. Therefore, it is difficult to identify the fault winding using the existing FRA model and the diagnosis method. In this paper, a distributed FRA model with turn unit was built based on split windings structure. And finite element method had been used to calculate the electrical parameters of transformer winding, especially for coupling capacitances and inductances of normal and misplaced disks. The comparison of the test and simulated results had verified the correctness of the model. According to this model, the typical axial displacement faults had been simulated. The results show that the frequency response curves of split windings shift more obviously than that of single winding below 100 k Hz. And the winding far from the core lead to a more significant influence on frequency response curves comparing to that near the core. A method had been proposed to identify the fault winding rapidly with the main feature.