Abstract: In this paper, the phenomenon of magnetoelastic bending is theoretically simulated for soft ferromagnetic rectangular thin plates in applied magnetic fields. A numerical program of 3d FEM is established to capture the nonlinear coupling intercationbetween magnetic fields and bending deflection. Afler the nonlinear characteristic of the bending deflection and the magnetic (field) force is quantitatively displayed, wediscuss the critical magnetic field and the effect of the incident angle of obliquely applied magnetic field on the critical field to the phenomenon of magnetoelastic instablitlity.