A network device, for supporting a power saving mechanism through an auto-negotiation of HDMI, includes a transmitting circuit and a receiving circuit. The transmitting circuit is arranged for generating a link pulse signal to a second network device, wherein the network device and the second network device perform the auto-negotiation of a network connection by using the link pulse signal through HDMI in order to support the power saving mechanism. After the receiving circuit of the network device receives another link pulse signal transmitted from the second network device through HDMI, the network device is controlled to be operated under the power saving mechanism.