This paper proposes an analytical method for calculating no-load stator iron loss of the surface-mounted permanent magnet synchronous motors with unequal teeth. The subdomain model is the theoretical core of this method. Based on this, harmonic effects are considered to calculate the vector magnetic potential and the distribution of the air gap magnetic field. The stator is divided into five regions: wide tooth, wide tooth tip, narrow tooth, narrow tooth tip and yoke, ensuring that the magnetic field variation laws in each region are basically consistent. Based on the relationship between air-gap flux density and stator magnetic density, the average magnetic flux density fluctuation functions of each stator region are obtained. Further calculate iron loss using the Bertotti model and verify the effectiveness of the proposed method through finite element analysis.