Along with the rapid expansion of Internet, the infrastructure of Internet is becoming increasingly complicated. Network topology discovering has becomes an effective way to research the Internet. The key point of network topology discovery is to discover the connectivity between Routers. Because Router usually has several network addresses, Router alias resolution is important to network topology discovering. In this paper, the alias merge of the router is specified and the key technology has been researched. Then a router alias discovery and merging algorithm is proposed. The algorithm gets the address aggregate through data analyses. The test shows that the actual connection of network can be obtained by the algorithm.