The purpose of this study was to examine whether the Reality Therapy applied Nuri-curriculum class is more effective than the existing Nuri-curriculum class in increasing prosocial behavior(sharing, helping, empathy and control, leadership) of preschool children. The participants of the study were 36 preschool children of the two classes, each consisting of 18 preschool children at the age of 5 of Y child-care center located at S Gu in Daegu City. One class was assigned into the experimental group, and the other the comparative group. Two instructional programs for a total of 8 sessions were constructed, one for the Reality Therapy applied Nuri-curriculum class and the other one for the existing Nuri-curriculum class, and implemented. The instrument used was the Prosocial Behavior Assessment Scale of Seo, So-Jung(2006). The research design employed was the pretest-posttest comparative group design. The data collected were analyzed using means, standard deviations, and analysis of covariance(ANCOVA) of the SPSS 22.0 program. The results were as follows. First, the Reality Therapy applied Nuri-curriculum class was more effective than the existing Nuri-curriculum class in improving preschool children’s sharing behavior. Second, the Reality Therapy applied Nuri-curriculum class was more effective than the existing Nuri-curriculum class in improving preschool children’s helping behavior. Third, the Reality Therapy applied Nuri-curriculum class was more effective than the existing Nuri-curriculum class in improving preschool children’s empathy and control behavior. Fourth, the Reality Therapy applied Nuri-curriculum class was more effective than the existing Nuri-curriculum class in improving preschool children’s leadership behavior. The results showed that the Reality Therapy applied Nuri-curriculum class would be more effective than the existing Nuri-curriculum class in increasing prosocial behavior of preschool children. The result implied that applying the Reality Therapy in employing the existing Nuri-curriculum should be considered for increasing preschool children’s prosocial behavior.