A data storage device includes multiple storage modules. Each storage module includes a storage which having a memory device and a first memory controller and a second memory controller. The first memory controller is coupled to the memory device for accessing the memory device. The second memory controller is coupled to the storage for accessing the storage. The first memory controller includes a first transmission interface. The second memory controller includes a second transmission interface. The first memory controller and the second memory controller communicate with each other through the first transmission interface and the second transmission interface.