The main objective of this paper is to investigate why university students use their smart phones in class and to develop a predictive model of smart phone use behavior that consisted of perceived benefit, perceived cost, attitude, social effect, intention, and habit. The proposed model is tested using survey data collected from 120 university student smart phone users. PLS analysis show as following: At first, intention and habit are significant predictors of smart phone use behavior in class. Secondly, perceived benefit and perceived cost as well as attitude and social effect are the factors affecting smart phone usage in class.