The invention relates to a method for scanning the relative displacement among focus light spots on a lens focal plane. The method is characterized in that the in-plane displacement of a focus lens is used for replacing the prior light beam angle scanning to realize linear scanning of the focus light spots on the lens focal plane. The resolution of the light spot scanning method is only determined by the resolution of a linear translation platform, is unrelated to the focus distance of the focus lens and can reach the angstrom magnitude. When the light spots are scanned, the optical distance of the light beam can be kept unchanged. The principle is disclosed as the figure. The focus lens is cut along the diameter and divided into two semi-lenses, and the two semi-lenses are coplanar. Two beams of incident laser are parallel to a primary optical axis of the lens so as to eliminate various image differences caused by the inclined light beams. The two beams of laser are focused on the focal planes through the two semi-lenses which are cut and separated respectively. One semi-lens is fixed on a one-dimension or two-dimension linear translation platform and controlled by the translation platform to move in the plane so as to realize the scanning of the focus light spots of the laser beam of the semi-lens on the focal planes relative to the focus light spots of the other semi-lens. The test example applied to the electron self-rotation transmitting in a semiconductor shows the advantages of the method.