A method for detecting a message loop, a routing agent apparatus, and a networking system. The method for detecting a message loop includes: receiving a request message sent by a network element apparatus; acquiring routing information for sending the request message to a server apparatus; detecting whether a next-hop link for sending the request message in the routing information and a link for receiving the request message belong to a same link set; and sending a response to the network element apparatus that a message loop is detected, when it is detected that the link for sending the request message in the routing information and the link for receiving the request message belong to a same link set. The technical solutions disclosed herein can improve the efficiency of detecting the message loop and thus have strong practicability.