A motherboard module having switchable PCI-E lanes includes a CPU, a first PCI-E slot, a second PCI-E slot, a first switch, and a second switch. 1st to a-th processor pin sets of the CPU are switchably electrically connected to 1st to a-th first PCI-E pin sets of the first PCI-E slot or (2N−a+1)th to 2N-th second PCI-E pin sets of the second PCI-E slot via the first switch to form PCI-E lanes whose number is a. (a+1)-th to 2N-th processor pin sets of the CPU are connected to the second input terminal of the second switch, and the second output terminal of the second switch is switchably electrically connected to (a+1)-th to 2N-th first PCI-E pin sets of the first PCI-E slot or 1st to (2N−a)th second PCI-E pin sets of the second PCI-E slot to form PCI-E lanes whose number is 2N−a, wherein 1