The purpose of this study was to investigate the effects of socio-demographic variables, family emotional environment and maternal discipline style on school children's emotional regulation. Subjects of this study consisted 953 elementary school students drawn from 4 elementary schools in Cheong-ju city and Cheongwon-gun. Data were analyzed by the methods frequency, percentage, Cronbach's ${\alpha}$, factor analysis, Pearson's correlation, and hierarchical regression using SPSSWIN 12.0 program. The results of this study were as follows: First, girls used greater problem-focused coping than boys did. Children in sixth grade used more problem-focused coping regulation compared to those in fourth grade. When children perceived higher level of family communication, emotional support, participation of family rituals, family worries, and parental conflict, they were more likely to use problem-focused coping. Additionally, both maternal supportive discipline and behavioral controlling discipline styles increased children's problem-focused coping. Second, girls presented greater emotional venting than boys did. Children in sixth grade expressed higher level of emotional venting compared to those in fourth grade. While family communication, family worries, and parental conflict increased children's emotional venting, family emotional support and participation of family rituals decreased it. Only mothers' psychological controlling discipline positively predicted children's emotional venting. Third, girls presented higher level of children's aggressive expression than boys did. The lower level of family support increased children's aggressive expression. Higher level of family worries and parental conflict increased it as well. Also, children's aggressive expression was positively predicted by mothers' psychological controlling discipline. Fourth, girls presented greater avoidance than boys did. Children in sixth grade expressed higher level of emotional avoidance compared to those in fourth grade. In family emotional environment, while family support lowered children's emotional avoidance, family worries and parental conflict increased it. Moreover, mothers' psychological and behavioral controlling discipline styles positively explained children's emotional avoidance. In conclusion, family emotional environment was the strongest factor to predict school children's emotional regulation among other variables.