With the proportion of renewable power sources increases, the modern power system is now experiencing a more diversified and efficient development, traditional electromagnetic equipment needs to be more optimized and improved to meet the new development trend. The multifunctional magnetically controlled transformer (MCT) organically integrates the magnetically controlled reactor with the distribution transformer. It has the advantages of fast and smooth adjustment of reactive power, and small overall floor area. Because of the topology of MCT is complex and affected by DC current, the analysis of electromagnetic and core loss characteristics on MCT iron cores is rather necessary. Firstly, this paper studied the structure and operating principle of MCT through the circuit analysis; Then, established the instantaneous core loss calculation model; Finally, analyzed the electromagnetic characteristics and electrical functions of MCT, further calculated its core losses via finite element analysis (FEA), providing reference for MCT heating assessment and design optimization.