In this paper, a kind of Magnetic Shape Memory Alloy (MSMA) model based on hysteretic nonlinear theory was developed. Von del Pol nonlinear difference item was introduced to interpret the hysteresis phenomenon of strain-magnetic field intensity (MFI) curve of MSMA. The final relationship among strain, stress and magnetic field intensity was obtained in partial least-square regression method to describe the variation of strain-MFI curve with stress. The result of forecast test shows that the model can describe the characteristics of MSMA in different stress well. The new MSMA model is easy to be analyzed in theory, which is helpful to application of MSMA in engineering fields.