The purpose of this paper is to present an Analytical Predict the Electromagnetic Field Density in surface mounted permanent magnet synchronous motors based on a subdomain field model. In this paper, which is one of a series of four, a 2-d analytical method for predicting field distribution in one SMPMSM is presented. In the presented method, Maxwell’s equations have been solved in different regions in pseudo-Cartesian coordinates system taking into account the non-homogeneous boundary conditions. The domain of the magnetic field is divided into four subdomains, viz. magnets, air gap, stator core and outer region. The governing equations and the boundary conditions to the interfaces between these subdomains are formulated in polar coordinate. The analytical prediction is validated by corresponding finite-element method. In future articles, we intend to study the effect of eccentricity on the distribution of magnetic fields in all areas of the motor at one slot less permanent magnet motor.