Abstract: Based on thermodynamics theory and equivalent inclusion principle, a force-magnetic coupling mesoscopic model of NiMnGa alloy/epoxy resin (NiMnGa/ER) composites including mechanical energy, chemical free energy, magnetocrystalline anisotropy energy, Zeeman energy and hardening fuction of reorientation process was derived. The stress-strain curves of the composite were simulated under zero magnetic field and compared with the test results. Finally, the stress-strain curves under different magnetic field intensities and angles (angle to stress direction, 0°, 45°) were predicted. The results show that the critical stresses of the reorientation of martensitic variants in the composites were 39.2 MPa, and of the reverse reorientation were 41.8 MPa, and the relative errors with the test results were all no more than 1.2%, verifying the accuracy of model. The stress-strain hysteresis loop of the composite at 45° magnetic field angle was larger than that at 0° magnetic field angle. When the magnetic field angle was 0°, the greater the magnetic field intensity, the greater the stress-strain hysteresis loop.