This paper develops the scalable analytical model (SAM) for predicting the performance of the surface-mounted permanent-magnet (SPM) machine with the arbitrary magnet shape and magnetization direction. The magnets are finitely divided into rectangles based on the magnetization direction and then they are replaced by the equivalent magnet currents along the surface of the magnets. Based on the SAM, the air-gap field of the SPM machine can be obtained considering the iron nonlinearity. The proposed method is useful for accelerating the optimization process of the torque ripple reduction in the servo motor application. The finite-element method (FEM) is carried out to verify the effectiveness of the proposed method.