The problem of non-linear magneto-elastic vibration is studied in this paper The motion equation of magneto-elastic coupling for a thin plate in the magnetic field is obtained using the principle of virtual work. According to the basic hypothesis of magneto-elasticity and Maxwell field equation, the expressions of electromagnetic force and torque in this equation are given. As an example, an approximate analytic solution of nonlinear vibration for a plate strip in lateral magnetic field is obtained by the multi-scale method. The influence of magnetic intensity on the period and the amplitude of vibration is discussed. It is shown that the vibration of a conductive thin plate under the action of a magnetic field is controllable through adjusting its parameters.