To improve the efficiency of alias resolution in large scale network, a concept of alias filtering is proposed based on IP level topology measured by traceroute. The characteristics of alias relationship are explored theoretically, and three attributes are proposed to deal with traceroute data based on the characteristics. Then, an alias filtering algorithm called AF and a verification of alias filtering algorithm called VAR are put forward. Finally, both the algorithms are verified via the traceroute data from Internet covering China, Japan, and Korea, which are measured by Skitter of CAIDA (Cooperative Association for Internet Data Analysis). The results prove that the concept of alias filtering is very important and the algorithms proposed in this paper are valid and efficient.