When the high-speed permanent magnet starter-generator (PMSG) is operating, the permanent magnets will be aff ected by high centrifugal forces. It is necessary to add a sleeve to protect the rotor and interference fi t with the permanent magnet. However, the performance of the high-speed PMSG will be signifi cantly infl uenced by the electromagnetic characteristics of the sleeve material. In this paper, a high-speed permanent magnet starter-generator for the micro-gas turbine is used as an example, and the two-dimensional fi nite element model is established. The correctness of the model is verifi ed by comparing the experimental data with the calculated data. Taking 10,000 r/min as the ignition speed, the diff erences of motor starting performances when using diff erent sleeve materials are compared. Secondly, decoupling the complex coupling torque in the starting process, the infl uence of material electromagnetic characteristics on the asynchronous torque and braking torque is determined, and the infl uence mechanism of material electromagnetic characteristics on the torque characteristics of highspeed PMSG is revealed. In addition, the eff ects of the sleeve materials on the output performance and loss of the high-speed PMSG are determined, and infl uence mechanism is revealed. On the basis, a sleeve multiplexing scheme is proposed to improve the starting performance while reducing the eddy current losses in the generating state. The results of the study provide reference and theoretical value for the optimization of high-speed permanent magnet starter-generator.