Abstract. The open and anonymous nature of peer-to-peer system makes it easy to be attacked and abused by some malicious nodes, so it is very important to establish a perfect trust mechanism in peer-to-peer environment. In this paper, we propose a novel group-based trust model in which the trust relationships between entities are divided into trust relationship in group and trust relationship between groups. This model deals with these two kinds of trust relationships in the different way and improves trust value calculation method. The model can get more real trust value at the small price, and the advantages of the model are simple structure and high reliability
