Link prediction is one of the research hotspots in complex network analysis and has a wide range of applications in both theory and reality. To improve the prediction accuracy, this paper proposes a new link prediction framework by considering both node similarity and community information, which overcomes the weaknesses of existing community-based prediction methods. In the proposed framework, a reasonable measure, called community relationship strength (CRS), is defined to estimate the closeness between communities. In this paper, we hold the view that the connection likelihood between two target nodes rests upon not only their similarity but also the closeness of communities that they belong to. Therefore, to measure the connection likelihood, the proposed framework combines CRS with traditional similarity indexes. Three CRS-based methods are derived from the framework. The performance of the CRS-based methods is comprehensively studied on 12 real-world networks compared with several groups of baselines. The experimental results indicate that the CRS-based methods are more effective and robust than others. INDEX TERMS Link prediction, community structure, similarity index, complex networks. I. INTRODUCTION A network is a structure that is composed of nodes and their static or dynamic relations, called edges or links. This simple structure can model a large variety of complex systems such as social, biological and technological systems, in which nodes are entities in these systems and links indicate the relations between entities [1]-[3]. The proliferation of data has inspired the study of network mining and complex network analysis. A wealth of interesting problems related to network mining, such as community detection [4], [5], node rank [6], and network embedding [7], have been studied. Among these interesting network-related problems, link prediction has been receiving increasing interest from disparate disciplines because not only many available real-world networks are incomplete [8], [9], but also its wide range of applications in both theory and reality [10], [11]. For examples, link prediction can be used in exploring network evolution mechanisms [12], [13], finding the cooperation opportunities among scientists [14], [15], recommending friends in social The associate editor coordinating the review of this manuscript and approving it for publication was Lin Wang.