A data center and an expansion method are provided to avoid a phenomenon of dense cables during data center expansion. In the data center, a first power device is connected to a computing device by using a bus, and a plug-in node and an idle electrical connection end are pre-disposed on the bus. In this way, when expansion is required, a second power device for expansion is directly added to the idle electrical connection end, and the bus is disconnected by using the plug-in node. In this way, the first power device and the second power device for expansion respectively supply power to the computing device by using two parts of the disconnected bus. According to this mode, no additional cable is required during the data center expansion, but an existing cable is directly disconnected to support power supply of a power device for expansion.