The invention provides a permanent magnet synchronous motor rotor assembly and a permanent magnet synchronous motor. The permanent magnet synchronous motor rotor assembly comprises a rotating shaft, a rotor yoke which is arranged around the periphery of the rotating shaft and includes a non-magnetic part, and a multi-pole magnetic ring which is arranged around the periphery of the non-magnetic part of the rotor yoke. Through improvement made on the rotor yoke and the ring magnet part of the permanent magnet synchronous motor rotor assembly, the counter electromotive force and air gap flux density of the stator winding of the permanent magnet synchronous motor are improved effectively, and the output torque and output power of the permanent magnet synchronous motor are improved. Moreover, the problem that the ring magnet is broken during running of the permanent magnet synchronous motor due to the difference in material expansion coefficient between the ring magnet and the magnetic part of the rotor yoke in the prior art is prevented effectively, and the reliability of the permanent magnet synchronous motor is improved.