Abstract: A novel type of permanent-magnet synchronous motor, driving Roots vacuum pumps for production line in Si-wafer fabrication, was designed in pole-slot matching scheme.The six poles and nine stator-slots, in the newly-designed small motor (1.5 kW and 9, 000 r/min), significantly weaken the negative impact of the higher-order harmonics on the performance and temperature-rise of the motor.In addition, the 3-D temperature profiles in the new motor was mathematically modeled, theoretically analyzed, numerically simulated and experimentally evaluated.The simulated results show that the highest temperatures of the components are much lower than Curie temperature of N35 SH permanent-magnet (150℃) .For example, the temperature ranges of the stator iron-core (38.69~40.05℃), coils (40.36~40.84℃) and permanent magnet (39.76~40.02℃) all meet the design requirements.The simulated and measured results were found to be in good agreement.