A trace layout of a printed circuit board (PCB) is provided with a north bridge, at least a peripheral component interconnect (PCI) slot, and an accelerate graphics port (AGP) slot. The PCB includes at least a first trace layer and a second trace layer under the first trace layer. The AGP slot is mounted between the north bridge and the PCI slot. The PCB further includes a number of first traces, and a number of second traces. The first traces are used for connecting the north bridge to the PCI slot while the second traces are used to connect the north bridge to the AGP slot. Some of the first traces are on the second trace layer under the AGP slot, while the other of the first traces are on the first trace layer or the second trace layer and trace aside the AGP slot. Most of the second traces are on the first trace layer and the other of the second traces are on the second trace layer.