The rare earth permanent magnet synchronous motor (PMSM) depends much on the rare earth permanent magnet materials. In order to solve this problem, a lessrareearth PMSM with Halbach array and module poles is proposed. The new structure of the rotor magnetic steel of the motor is described. The main pole of the rotor magnet is composed of two layers of permanent magnets, the outer magnet is made of NdFeB permanent magnet material, the inner magnet is made of ferrite permanent magnet material, and the auxiliary pole magnet is also ferrite permanent magnet material. The electromagnetic torque, the torque ripple and the cogging torque are regarded as optimization criteria. The motor parameters are optimized by using the number of permanent magnets per pole, magnetization angle, permanent magnet material and permanent magnet thickness. A chutetype stator structure is used to reduce cogging torque. The optimized lessrareearth PMSM with module poles reduces the amounts of permanent magnets and reduces the cost of motor while ensuring the torque performance. Finally, the finite element method is used to analyze the performances under the conditions of noload and rated load operation, and to verify the validity and reasonableness of the proposed motor.