Wireless network with ad-hoc behaviour consists of mobile nodes which facilitates a fundamental architecture for communication without any support of traditional, steady and fixed-positioned routers. However, the architecture must preserve communicating routes and hosts have mobile nature and their restricted transmission range. There are several protocols for managing the routing in the mobility atmosphere. In the MANET, the mobile nodes can perform the roles of both hosts and routers. Various MANET applications are used for Military strategic communications and Disaster recovery mostly depend on secure node communication. For Secure Communication, we use several Logical Hierarchy Key protocols in Mobile Ad-hoc Network but the group key administration looks upon many problems assuming due to unreliable media, mobile node failure cosplay kost?me and less energy resources. In this paper, we analyze new logical key with Optimal Probabilistic Technique in DSR and OLSR routing protocols in Mobile Ad-hoc Network. In this key, all nodes are shaped in a tree structure. OPLKH decreases the Rekey Cost and several routing energy consumptions in Mobile Ad-hoc Network. In simulation, we calculate the amount of Rekeys Cost, Energy Consumption for Data Transmission, Energy Consumption for Routing and Energy Consumption for Key Generation in the network.