Abstract: A storage system and a data transferring method thereof are provided. The storage system includes at least one drawer storage device, a backplane board and a processing unit. Each of the drawer storage devices accommodates at least one storage device, and has a first connecting interface. The backplane board has a second connecting interface. The backplane board and each of the drawer storage devices are connected with each other through a transmission line. The first connecting interface and the second connecting interface are connected or isolated with each other. The processing unit detects a connection status between the first connecting interface and the second connecting interface, and determines to transfer data through at least one of the transmission line and a connection between the first connecting interface and the second connecting interface according to the connection status.