Magnetorheological elastomers (MREs) are composed of silicone and iron powder so that they can possess ferromagnetic and viscoelastic properties. The shape and the stiffness of the MREs change depending on the magnetic field. Therefore, it is expected to be used for an artificial muscle or damping material. However, it is difficult to design because ferromagnetic and viscoelastic properties greatly change depending on ratio of the iron powder and strength of magnetic field. This paper presents a numerical method for MREs analysis by coupling a particle method with a finite element method (FEM), in which the nonlinearity of MREs as Young's modulus, Poison's ratio and stiffness is taken into account. The numerical algorithm is described and calculated results are shown.