The research subjects were 3 children asked by a childminder and selected through K-CBCL aggression scale and mother-reported aggression test, among those aged 6 and living in the child welfare facility located in B City. The program was implemented 2 terms a weak, 40 minutes for each term, being totally 12 terms, and each term consisted of beginning activity (10 min), main activity (20 min), and finishing activity (10 min). In order to learn about the effect of the physical activity-based emotion-regulation program on aggression of preschool child in the welfare facility, we conducted mother-reported aggression test before and after the implementation of the program, and filmed scenes of free playing after each term’s finished, and measured frequency of aggressive behaviors of children according to aggressive behavior observation report. The results of this study are as follows: first, The physical activity-based emotion-regulation program reduced aggression of all the 3 children in the child welfare facility on the aggression test reported by the childminder. second, The physical activity-based emotion-regulation program reduced aggressive behaviors (against persons, against things, language) of all the 3 children in the child welfare facility in the situation of out of the terms. Therefore, though this study had limitation to generalize the results, for it is an experimental research for a handful of cases, we could find that the physical activity-based emotion-regulation program reduced aggression of preschool child in the child welfare facility.