Large-scale mobile social networks (MSNs) facilitate communications through mobile devices.The users of these networks can use mobile devices to access,share and distribute information.With the increasing number of users on social networks,the large volume of shared information and its propagation has created challenges for users.One of these challenges is whether users can trust one another.Trust can play an important role in users\' decision making in social networks,so that,most people share their information based on their trust on others,or make decisions by relying on information provided by other users.However,considering the subjective and perceptive nature of the concept of trust,the mapping of trust in a computational model is one of the important issues in computing systems of social networks.Moreover,in social networks,various communities may exist regarding the relationships between users.These connections and communities can affect trust among users and its complexity.In this paper,using user characteristics on social networks,a fuzzy clustering method is proposed and the trust between users in a cluster is computed using a computational model.Moreover,through the processes of combination,transition and aggregation of trust,the trust value is calculated between users who are not directly connected.Results show the high performance of the proposed trust inference method.