Modeling dynamic user behavior over online social networks not only helps us understand user behavior patterns on social networks, but also improves the performance of behavior analysis tasks. Time-varying user behavior is commonly influenced by multiple factors: user habit, social influence and external events. Existing works either consider only a part of these factors, or fail to model the dynamics behind user behavior. Thus, they cannot precisely model the user behavior. We present a generative Bayesian model HES to model dynamic user behavior data.We take the influential factors and user’s selection process as separate latent variables, based on which we can recover the evolving patterns underneath user behavior data sequences. Empirical results on large-scale social networks show that the proposed approach outperforms existing user behavior prediction models by at least 8% w.r.t. prediction accuracy. Our work also unveils some interesting insights underneath social behavior data. Modeling dynamic user behavior over online social networks only only helps us understand user behavior patterns on social networks, but also improves the performance of behavior analysis tasks. Time-varying user behavior is often influenced by multiple factors: user habit, social influence and external events Since works either consider only a part of these factors, or fail to model the dynamics behind user behavior. We present a generative Bayesian model HES to model dynamic user behavior data. We take the influential factors and user’s selection process as separate latent variables, based on which we we recover recovering evove patterns underneath user behavior data sequences. at least 8% wrt prediction accuracy. Our work also unveils some interesting insights underneath social behavior data.