To meet the requirements of modeling the new modality of peer-to-peer（P2P）network applications which have been rapidly developing in the Internet recently, a formal description method for modeling multiparty concurrent network interactions is studied. The main characteristics and the classifications of P2P systems are discussed. Considering the requirements of P2P application modeling and referring to the component-based modeling thought, a description method based on communicating sequential processes （CSP）is proposed for the P2P network models. By using a CSP process group, this method can describe the dynamic interactive relationship which focuses on multiparty concurrent interaction of P2P systems more advantageously and accurately. The application of nondeterministic semantemes of CSP in describing the interactive relationship of P2P networks is discussed. The advantages and description abilities of the proposed method are demonstrated through the modeling of a new P2P media-on-demand system.
