Mobile Ad-hoc Network (MANET) is a collection of wireless mobile nodes which dynamically forms a temporary network without the use of any existing network infrastructure or centralized administration. The security in MANET is primary concern in order to provide protected communication between mobile nodes in a hostile environment. In this paper, we present the Secure Message Transmission (SMT) protocol, which safeguards the data transmission against arbitrary malicious behavior of other nodes in multipath environment. The goal of Secure Message Transmission (SMT) is to discover routes in ad hoc network and to ensure secure data forwarding, after the discovery of routes between the source and the destination and although such discovered routes may not be free of malicious nodes. It exploits the redundancy of multipath routing and adapts its operation to remain efficient and effective even in highly adverse environments. The basic idea is to transform a secret message into categories of information in multiple paths. The message and the redundancy are divided into a number of pieces, so that even a partial reception can lead to the successful reconstruction of the message at the receiver. We present the overall system architecture and algorithm for message dispersion and message transmission. We also consider the routing stability in Mobile Ad-hoc Network (MANET) because its environment is more selfish. So we extended the data dispersion along with multipath Optimized Link State Routing Protocol (OLSRP). Our simulation study shows that this approach is useful as it enhances the security in multipath routing Network.