The invention relates to a printed circuit board. The printed circuit board comprises a first reference layer, a first signal layer and a second signal layer which are layered, wherein the first signal layer is provided with a first differential pair which uses the first reference layer as a reference layer, the second signal layer is provided with a second differential pair, a first ground wire and a second ground wire are arranged in the second signal layer and symmetrically arranged on both sides of the second differential pair, the first differential pair is arranged above the first ground wire, and the second differential pair uses the first ground wire and the second ground wire as the reference layer. The printed circuit board arranges the second differential pair and the referencelayer thereof on the same layer to improve the wire distributing density of the printed circuit board, and because a ground wire is also arranged under the first differential pair, the interlayer interference can be further inhibited.