A bridging device and a power saving method thereof are disclosed. The disclosed bridging device includes a connector, a connection detector and a bridging chip. The connector is operative to connect to a host and includes a power pin and a command pin. The connection detector is coupled to the power pin to determine whether the connector is floating, and, outputs a linked signal when the connection is non-floating. The bridging chip is coupled to the command pin and the connection detector. When the bridging chip receives a power saving command transferred from the host via the command pin and the linked signal transferred from the connection detector, the bridging chip executes a power saving operation.