A method for checking signal transmission lines of a printed circuit board (PCB) layout includes determining differential pairs to be checked and dividing the differential pairs to be checked into a first group and a second group. A first reference distance between differential pairs belonging to the same group and a second reference distance between differential pairs belonging to different groups are set. A first box surrounding each line section of one to be checked signal differential line of the first group and a second box surrounding the first box are created. One first box surrounding each line section of the to be checked differential line of the second group is created. Whether or not in the first box and the second box there are differential lines which do not satisfy design standards is determined.