In the method and device for discovering a network topology provided in embodiments of the present application, there is no need to collect multiple types of network characteristic data, which reduces consumption of network resources and can improve accuracy of discovering a network topology. The particular solution is: collecting state information of all ports of a network element of a to-be-analyzed network and deleting a port in a normally-closed state to obtain a required port set; acquiring a link set of each port in the port set and a similarity value of state information of two ports included in all links in the link set; setting a link with a maximum similarity value in the link set of each port as a candidate link of each port; and acquiring a network topology of the to-be-analyzed network according to the candidate link of each port.