Information retrieval(IR) over peer-to-peer(P2P) network has attracted a lot of research interests because of its decentralization, self-organization and scalability. As semantic IR faces challenges in centralized information systems, semantic IR over P2P network is far challenging: 1.It's costly or impossiblel to have a global knowledge in P2P network, which is often important to semantic IR, such as LSI. 2. It's hard to locate the documents semantically relavant to a query efficiently. We present our motivation and research focus in this poster.