This study aims to elucidate the mediated effect of emotional clarity, ambivalence over emotional expressiveness in the effects of the maternal reaction to children’s negative emotions on relational aggression. The participants in this study were 377, 5th and 6th grade in elementary school and completed a set of questionnaires consisting of maternal reaction to children’s negative emotions, emotional clarity, ambivalence over emotional expressiveness, relational aggression. To verify the relation between variables and the mediating effect, it was analyzed structural equation model by using SPSS 21.0 and AMOS 21.0. As a result, first, the mother’s negative reactions to children’s negative emotions were positively correlated with relational aggression and ambivalence over emotional expressiveness and negatively corelated with emotional clarity. Second, emotional clarity mediated the relation between maternal negative reaction to children’s negative emotions and relational aggression. Third, ambivalence over emotional expressiveness partially mediated the relation between maternal reaction to children’s negative emotions and relational aggression. That is, it confirmed that the mother s reaction to children’s negative emotions have direct influence on relational aggression and indirect influence through emotional clarity and ambivalence over emotional expressiveness. Lastly, we discussed the implications limitation of this study.