For high-speed permanent magnet (PM) electrical machine, the PM material has very small tensile stress, and it can’t withstand the huge centrifugal force. So, a high-strength sleeve with interference fit is necessary to protect the PM. This paper mainly analyzes the strength of rotor sleeve and PM. It deduces the theoretical calculation method of the strength according to Lame equation, and it also analyzes the stress of sleeve and PM by ANSYS Workbench. The result show that the theoretical calculation value is closely to the ANSYS result, and it can meet the requirements of protecting the permanent magnet in high rotation speed.