Provided is an MRA (multi-root aware) PCI express switch accommodating a plurality of root complexes. The MRA PCI express switch includes: a setting register storing necessary information to set a PCI tree based on a switch connection topology and a physical connection state; and a virtual switch bridge controller storing necessary information to establish a virtual PCI tree, irrespective of a status of the setting register. The root complexes can be booted based on the information in the virtual switch bridge controller.