The main purposes of this study are to realize the current condition of primary school teachers’ adopting mobile instant messenger (MIM), LINE, to carry on parent-teacher communication, and to explore the correlation among positive and negative influencing factors, behavioral intention and behavior of use for teachers' acceptance. Based on united theory of acceptance and use of technology 2 (UTAUT 2), perceived risk and anxiety of message receiving and sending were added in research framework. The subjects of this study were public primary school teachers. 450 questionnaires were distributed and 437 were retrieved, with return rate 97.1%, valid for 430 copies and valid return rate 95.6%. The findings of this study were summarized as follows. There is a significant positive effect of performance expectancy, social influence, and facilitating conditions on behavioral intention; there is a significant negative influence of perceived risk as well as anxiety of message receiving and sending on behavioral intention. There is a positive significant effect of behavioral intention and facilitating conditions on behavior of use.