Relay routing system consists of a set of relay routers, providing relay routing for routing domains that cannot exchange routing information. The key point of the system is to configure appropriate relay router for routing domains. In this paper, all the relay routers are taken as a virtual node by assigning them an anycast address which is accessed along the shortest path by anycast routing. In addition, source routing is used to route the data packets to relay router. The anycast-based relay routing system enables auto-configuration of relay routing,improves the performance and the reliability of relay routing, and it is compatible with existing network infrastructure with quite low overhead.