A storage expansion apparatus, comprising: a quick path interconnect, QPI interface module, which communicates with a central processing unit, CPU through a QPI bus; a peripheral component interconnect express, PCIe interface module, which communicates with the CPU through a PCIe bus; an interface selecting module, connected to the QPI interface module and the PCIe interface module separately; a system management bus, SMbus selecting module, connected to the interface selecting module, and configured to send a selection instruction to the interface selecting module, so that, according to the selection instruction, the interface selecting module chooses to receive the QPI protocol transaction that is obtained by the QPI interface module and sent by the QPI interface module; or chooses to receive the QPI protocol transaction that is obtained by the PCIe interface module and sent by the PCIe interface module; or chooses to receive the processed PCIe protocol storage transaction sent by the PCIe interface module; a home agent, HA module, connected to the interface selecting module; and a memory controller engine, MCEng module, connected to the HA module and the interface selecting module separately; wherein when the storage expansion apparatus serves as a storage IO interface device, the PCIe interface module is configured to receive PCIe data sent through the PCIe bus, process a PCIe protocol storage transaction in the PCIe data, and send a processed PCIe protocol storage transaction to the MCEng module through the interface selecting module, and the MCEng module implements a read/write function and provides an interface for connecting to a storage IO device, wherein the storage IO interface device is a hard disk or a solid state disk; when the storage expansion apparatus serves as a memory expansion device, the QPI interface module is configured to receive QPI data sent through the QPI bus, obtain a QPI protocol transaction in the QPI data, send the QPI protocol transaction to the interface selecting module, and then output the QPI protocol transaction in the QPI data to the HA module through the interface selecting module; the HA module processes the QPI protocol transaction in the QPI data, and sends a processed QPI protocol transaction to the MCEng module; and the MCEng module implements a read/write function and provides an interface for connecting to an expanded memory; and when the storage expansion apparatus serves as a memory expansion device, the PCIe interface module is configured to receive PCIe data sent through the PCIe bus, obtain a QPI protocol transaction in the PCIe data, send the QPI protocol transaction to the interface selecting module, and then output the QPI protocol transaction in the PCIe data to the HA module through the interface selecting module; the HA module processes the QPI protocol transaction in the PCIe data, and sends a processed QPI protocol transaction in the PCIe data to the MCEng module; and the MCEng module implements a read/write function and provides an interface for connecting to an expanded memory. a quick path interconnect, QPI interface module, which communicates with a central processing unit, CPU through a QPI bus; a peripheral component interconnect express, PCIe interface module, which communicates with the CPU through a PCIe bus; an interface selecting module, connected to the QPI interface module and the PCIe interface module separately; a system management bus, SMbus selecting module, connected to the interface selecting module, and configured to send a selection instruction to the interface selecting module, so that, according to the selection instruction, the interface selecting module chooses to receive the QPI protocol transaction that is obtained by the QPI interface module and sent by the QPI interface module; or chooses to receive the QPI protocol transaction that is obtained by the PCIe interface module and sent by the PCIe interface module; or chooses to receive the processed PCIe protocol storage transaction sent by the PCIe interface module; a home agent, HA module, connected to the interface selecting module; and a memory controller engine, MCEng module, connected to the HA module and the interface selecting module separately; wherein