The multi-path routing scheme provides reliable guarantee for mobile ad hoc networks. This paper proposes a new method used to analyze the security of multi-path routing protocol within the framework of Universally Composable (UC) security. Based on the topological model that exist in adversarial nodes, the concept of plausible route is extended and the definition of plausible-route set is presented. Plausible-Route set is used to describe the multi-path routing for ad hoc networks, and a formal security definition based on UC-RP is given. A provably Security Multiple Node-Disjoint Paths source routing (SMNDP) is proposed and used to address secure fault issue of MNDP (multiple node-disjoint paths) in the active adversary model. The new approach shows that the security of SMNDP can be reduced to the security of the message authentication code and the digital signature. SMNDP implements the correctness of route discovery process, the authentication of nodes identifier and the integrality of route information.