With the broad implementation of Internet, VoIP poses an important role on the Internet and provides a new way to people to contact each other. As VoIP's cheapness and simpleness, many institutes forecast that VoIP emerges as next spam entryway like e-mail service. In this paper, we propose a novel schema, called P2P-AVS (anti-voice-spam), against spam call on the VoIP networks. It bases on an open distributed architecture to store and share end users' personal evaluation about spammer. P2P-AVS system acts as a middleware of VoIP proxy server, and constructs a DHT network over them to make it more robust. Furthermore, we design a proper reputation model to measure user's histoy and combine others' evaluation so that we can detect spam calls. At last, we verify the reputation model through building simulation testbed. Results show that reputation model of P2P-AVS could detect spam calls accurately.