<p>Disclosed is a method for diameter routing. The method includes: after a call between a Code Division Multiple Access (CDMA) network user and an Internet Protocol Multimedia Sub-system (IMS) user is established, in the process of sending charging information to an IMS network, the user number of the IMS user is utilized as a main keyword of a diameter message routing for seeking a route. Also disclosed are a diameter routing system and a Media Gateway Control Function (MGCF) device. The present invention does not need to set the correspondence between a user number and a Charging Gateway (CG) domain name in the IMS network element, and does not need the IMS network element to send the CG domain name obtained according to the user number to the MGCF network element during the call process, thereby reducing the message traffic.</p>
