Accurate analysis of the influence of the motor structure and magnetic saturation on the air-gap magnetic field distribution is the key to the design and optimization of permanent magnet motor. Taking the fractional slot concentrated winding interior permanent magnet synchronous motor (FSCW-IPMSM) as the research object, the analytical model of no-load permanent magnet magnetic field considering rotor magnetic bridge leakage and the analytical expression of armature reaction magnetic field are obtained respectively based on the magnetic circuit analysis method and the distribution law of FSCW. Considering the stator slot structure and the permanent magnet distribution in the rotor, the influence of stator slot and rotor salient pole on the air-gap magnetic field is taken into account by relative air-gap permeability. Combined with the B-H magnetization curve of the stator core material and the local magnetic saturation characteristics of the stator core, the core equivalent magnetic resistance and dynamic permeability are introduced to consider the effect of the stator core magnetic saturation on the loaded air-gap magnetic field. Finally, the results of finite element simulation and prototype test verify the accuracy of theoretical analysis. It provides a theoretical basis for the electromagnetic design and performance analysis of this type of motor.