Teaching involves immense amounts of emotional labor. However, there is a lack of research on teachers´ emotional labor. The primary purpose of this study was to explore the psychological processes in emotional labor of elementary school teachers, including their interactions with students, parents, administrators, and colleagues. Specific goals of the study included：(1) to analyze the causes of positive emotional expression through surface acting and deep acting, and (2) to understand the psychological processes of how teachers regulate their negative emotion. A qualitative approach using grounded theory strategy was used to explore the research question, through in-depth interviews with 18 elementary school teachers. Results showed that teachers expressed positive emotions by surface acting, mainly because of the courtesy exchange and personal status, whereas positive emotions display by deep acting, were mainly due to teaching needs, professional identity, and personal trait. The suppression of negative emotion was for many reasons, including avoiding regret, considering consequences, ethical compliance, empathy, personality cultivation, and professional maturity. The outbreaks of negative emotions were due to exceeding tolerance limit and using strategies. Teachers expressed negative emotions in classroom management for the purposes of warning, and avoiding hurt. Implications for future research are discussed.