Taking into account the influence of structural deformations on electromagnetic field,assuming that the beam's deformations are small,and regarding the change of current direction after beam's deformations as current vector's stiff rotation, the natural lateral vibration control equation of beam carrying electric current in magnetic field was established. The equation indicated that the beam's natural lateral vibration was a typical issue.The perturbation method was employed to get the control equation's approximate solution.The analytical expressions of beam's natural lateral vibration frequency and displacement were derived.The main factors, such as the distance of wire and beam, the quantity and direction of current, and the length and radius of beam,which affect the natural lateral vibration of beam carrying electric current,were discussed with an example,and some valuable conclusions were obtained from the example.