The rotor under study is a PM rotor of a synchronous machine intended for operation at 60 000 rpm. It is well known that design of high speed permanent magnetic (PM) rotor is quite different from that of a normal PM rotor. The determination of the rotor structure and dimensions must take consideration of the strength, stiffness and the magnetic properties of the PM rotor. Based on the Riccati transfer method, the dynamic model of the rotor-bearing system has been established. Then the supporting stiffness of the magnetic bearing is estimated and the PM rotor’s critical speeds and the corresponding vibration modes have been found. A prototype has been built and some test results proved the correct of the calculation.