Bayesian Network (BN), as a directed probabilistic graph model, provides consistent, theoretically solid mechanisms for processing uncertain information and solves both classification and regression problems. The use of BNs has become widespread because of their intuitive appeal to model variable dependency relationships. It is an ideal tool for causal relationship modeling and probabilistic reasoning. BN is a fundamental tool in modeling [7] [8], Prediction [9] [10] [11] and risk analysis [12]. BNs have been applied in a wide range of areas such as Health Care, Education, Finance, Environment, Telecommunication, and Information Technology. Modeling social circle with Bayesian network has the unique advantage of quantitatively predicting user’s social circle existence with probability and running query with incomplete values.