A storage expansion system includes an expansion apparatus and a serial advanced technology attachment dual in-line memory module (SATA DIMM) device. A memory slot, a SATA port, a SATA signal expansion member, and a voltage converter are arranged on the expansion apparatus. The memory slot includes first power pins, first ground pins, and first signal pins connected to the SATA signal expansion member. A first edge connector is arranged on a side of the expansion apparatus. The first edge connector includes second power pins and second ground pins. The first and second power pins are connected to the voltage converter. A second edge connector is arranged on a bottom side of the SATA DIMM device. The second edge connector includes third power pins connected to a control chip and storage chips, third ground pins, and second signal pins connected to the control chip.