The present invention discloses a permanent magnet synchronous motor, a rotor thereof comprising an iron core in cylindrical form, with p S pole magnet plates and p N pole magnet plates arranged inside of the iron core around an axis thereof, wherein p is a positive integer, and the p S pole magnet plates and the p N pole magnet plates are alternatively aligned; on a surface of a rotor iron core of each magnet steel plate are arranged two d axial surface grooves; the two d axial surface grooves corresponding to each magnet steel plate are situated on two sides of a center line of the magnet steel plate; an inter-axial distance of the two d axial surface grooves of each magnet steel plates is approximately equal to a tooth tip span of a rotor tooth of the permanent magnet synchronous motor. The present invention also discloses a rotor of a permanent magnet synchronous motor. The permanent magnet synchronous motor and the rotor of the present invention reduces torque ripple in the torque area, has a simple structure and low cost, and is easy to manufacture.