The purpose of this study is to examine the relationship between maternal self-reflection, infant’s effortful control, maternal response to negative emotions, and to verify the mediating effects of maternal response to negative emotions in the effect of maternal self-reflection on infant's effortful control. The maternal response to negative emotions was divided into supportive and non-supportive responses, and since they have opposite meanings, the mediating effect was verified by dividing them. In this study, 230 questionnaires were collected from the mothers with Infant aged 3 to 6, and a total of 214 copies were analyzed, excluding 16 copies that were unfaithfully answered. The main results of this study were as follows. First, the maternal self-reflection, the infant’s effortful control, and the maternal supportive response to negative emotions all showed a significant positive correlation. On the other hand, there was a significant negative correlation with the maternal non-supportive response to negative emotions. Second, in the effect of maternal self-reflection on infant’s effortful control, the partial mediating effect of maternal supportive and non-supportive responses to negative emotions was verified. These results suggest that the more self-reflection a mother makes, the more supportive the child is, which also affects the infant’s effortful control.