Abstract: Instant messaging (IM) system has become primary communication tools between people. In order to design a more friendly instant messaging system, it is necessary to understand how the friend relationships are built and evolved in the real instant messaging system. This paper studied the characteristic of friend relationships in network and the trend of making friends with other QQ users and considered nodes in degree and out degree of actual QQ users. At the same time a new algorithm for IM topology was proposed by considering the influence of both node property and the trend of making friends of QQ users. We call it Attributcbased model (AI3M) which is different from traditional rules in which node degree is top-priority. I}he experiments show that AI3M behaves better than 13A algorithm when friend relationship is considered.

Key words: User property,Instant messaging system, Topological evolution,l3A modcl,Laplacian spectrum