A method for disposing power planes and ground planes of a printed circuit board (PCB), said method comprising the steps of: providing a PCB on which is disposed with a geometric layout and a via hole; providing a line on said PCB for intersecting said geometric layout to form a plurality of points of intersection; defining line segments by segmenting said line at each of said points of intersection to form a plurality of line segments; deleting some of said line segments having one end not being point of intersection for said geometric layout to form a plurality of segmented regions; searching a closed region by repeatedly searching region from any one of the points in said plurality of segmented regions; determining whether a closed region is a smallest closed region; determining whether a via hole is located within said smallest closed region.