Abstract: In the research of electric power system relay protection, the research on the sympathetic inrush current, especially the engineering application, is very few.However,with the occurrence of many accidents caused by the sympathetic inrush current at home and abroad, more and more scholars have gradually paid attention to it. In this paper, the complex sympathetic inrush current model of transformer which is in line with the actual operation is studied. The time-domain expression of flux linkage is obtained by Laplace and inverse Laplace transforms, and the mechanism of complex sympathetic inrush current is analyzed. Finally, an example of misoperation is used to confirm the characteristics of the sympathetic inrush current, and the influence of the sympathetic inrush current on the power transmission and the waveform analysis method of the micro-electric network is fully explained.