Abstract: In mobile Ad-hoc networks (MANETs), due to their anonymous and self-organization nature mobile nodes have to manage the risks involved in the transactions without prior knowledge about each others reputation. The sample space of evidence may be not integrative or reliable because of the change of network topology or the occurrence of wireless collision, so the existing trust evaluation models cant be applied. To solve the problem of trust evaluation and establish the trust relationship between nodes, CFSTrust, a subjective trust management model, is proposed to quantify and evaluate the trustworthiness of nodes. Its mathematical description and implementation are also given. The fuzzy-similarity and certainty-factor are used to model the issues of trust management. The evaluation of subjective trust is discussed, the derivation rules of recommendation trust relationships in MANETs are presented and a subjective trust management model is provided. Theoretical analyses and experimental results show the model is more effective compared with the trust model based on evidence-evaluation (TrustNet). The formal model proposed provides a new valuable way for MANETs environments.