The purpose of this study was to examine the development of children's emotion regulation that expression corresponding to the feeling of other person and also to examine the reason of emotion regulation. Subjects were boys and girls students in 1st(N=40), 3rd(N=37), 5th(N=35) grade. Subjects were asked about the facial expression of a protagonist when that is facing a friend with express happiness, sadness and anger. Also subjects were asked to answer the suitable reason that the protagonist regulated the emotion (prosocial, self-protect and norm). Results revealed that happiness and sadness did not have the age difference. However, as for anger, the third grader and the fifth grader showed the same feeling as other persons like the adult. On the other hand, a first grader does not show the same feeling as other persons.