Cooperative Communication is a technique that allows multiple node to transmit the same data. In this paper propose a Cooperative Shortest Path (CSP) Routing Algorithm for Mobile ad hoc Network (MANETs).Cooperative Shortest Path (CSP) routing algorithm that uses the Dijkstra's algorithm as the basic building block and reflects the cooperative transmission. The objective of Cooperative Shortest Path (CSP) Routing Algorithm is to improving the network lifetime and archives higher energy saving and better balanced energy consumption among network nodes, especially the network is large scale. Our empirical results indicate so as to among more nodes added in the network, more energy saving can be achieved by cooperative routing since a dense network.