The lack of customer trust is an important lagging factor for the development of C2C Ecommerce. Building reputation evaluation mechanism is an effective way to solve the C2C trust management problem. However, the reported reputation evaluation models have several disadvantages in evaluation dimensionality and can not satisfy the demand of China’s C2C Ecommerce. To solve the above problem, a multidimensionality reputation evaluation model for C2C Ecommerce is proposed. In this model, the factors which can show seller’s reputation are classified into two dimensionality types: transaction dimensionality and agency dimensionality. The former includes four dimensionalities, i.e. transaction time, transaction fee, buyer reputation and fraud punishment; the latter includes two dimensionalities, i.e. business federation, plan of customer safeguard. Moreover, C2C seller’s reputation can be massed into a twovariable set and provided as an evaluation target to customers for their purchase decisionmaking. The empirical study on taobao.com shows that the proposed model has better capabilities of reputationdistinguishing, antireputationdenigrating, antireputationcolluding and fraudpunishment than that of traditional model.