A method for diagnosing an access node (AN) is provided, including: a service node (SN) sending a diagnosis query message to the AN; after receiving the diagnosis query message, the AN returning a diagnosis query response message to the SN; and the SN displaying a query result on a command line or sending the query result to a network management system. A system for diagnosing an AN is provided too. The method and system solve the communication problem between the network system, maintenance group or operator associated with the SN and the network system, maintenance group or operator associated with the AN. As a result, the diagnosis of the AN is fast and efficient, thereby improving the diagnosis efficiency during the network failure and subscriber service failure.