System and methods for object clustering are provided. The system may determine a weight of a directed edge between nodes of a directed network graph. The weight may represent a similarity degree of target objects associated with the target nodes. The similarity degree may reflect strength of an association between the two target objects, and further reflect a possibility that the two target objects belong to the same clustering category. After the directed network graph is constructed, nodes in the directed network graph may be clustered based on weights of directed edges between the nodes in the directed network graph.