A method for laying out a circuit board includes following steps. A substrate board is formed with a plurality of board sides. A ground plane, including a plurality of tiles, is provided. Each ground trace tile is defined by a plurality of ground traces. A signal plane on the substrate board has a plurality of signal traces that comprise of a plurality of straight line segments. Any one ground trace of each tile is arranged at an angle other than zero degrees relative to one determined board side. The straight line segments is applied to be mapped on the ground plane crossing one ground trace of one tile within an angle range determined by the ground traces of the tile and an adjacent diagonal line of the tile. The one ground trace and the straight line segments are applied at an angle movable in a range from 22.5° to 32.5°.