The embodiment of the invention provides a port extending device and a stacking system, and relates to the technical field of communication. The port extending device comprises more than one uplink ports and multiple switching chips; each uplink port comprises multiple internal connection points and external ports; the multiple internal connection points are electrically connected with the external ports; each switching chip is electrically connected with more than one internal connection points of each uplink port in a circuit board wiring manner; the external ports are used for pluggable connection of an optical module; and thus, the multiple switching chips communicate with the optical module and an external control device through the external ports of the uplink ports. Because each switching chip in the port extending device is electrically connected with each uplink port, communication between the external control device and all the switching chips can be realized only through fewuplink ports and optical modules on the port extending device, even through an uplink port and an optical module; and thus, the hardware cost is effectively reduced.