Due to its material characteristics and microstructure, soft magnetic composite (SMC) material has the advantages of low eddy current loss coefficient, isotropy and so on. It is suitable for the design of ultra-high-speed permanent magnet synchronous motor (PMSM), which can effectively reduce the motor iron loss. Taking a PMSM with a rotation speed of 4 000 r/min and a frequency of 533.33 Hz as an example, the comparison analysis and finite element simulation calculation of SMC materials and silicon steel sheets are carried out from the aspects of electromagnetic properties and iron loss analysis. The validity of SMC material analysis results is verified by prototype test. The analytical method is used and a 120 000 r/min ultra-high-speed PMSM using SMC material is taken as an example to compare and analyze the influence of different pole and slot matching on electromagnetic performance. It provides certain guidance for the application of SMC materials to ultra-high-speed PMSM.