Abstract: Based on the features of delay tolerant network (DTN), mobile social network (MSN) uses “storage-carry-forwards” approach for message transmission between nodes. How to select a suitable relay node for efficient message transmission is an urgent issue in the current research fields. This paper focuses on the problem by analyzing the social characteristics of network in different perspectives. Firstly, based on the interaction between nodes, the model of social relations between nodes is constructed. Secondly, this paper gives the definition of neighbor set and local community based on the network topology and establishes the community relationship between the nodes. Furthermore, this paper defines the social activity based on the behavior of nodes and takes advantage of the PageRank algorithm to obtain PR values on the basis of multiple features of nodes. Then, transmission values of nodes is defined by using PR values and different utility values of nodes can be obtained. On this basis, considering community relations of nodes and different transmission utility values of nodes, this paper designs and implements a message transmission algorithm in mobile social network. Finally, experiments show that the algorithm has advantages in delivery ratio, overhead ratio and average delay.