The purpose of this study was to analyze the process of child-centered play therapy for three preschoolers with separation anxiety qualitatively and it’s effect quantitatively. The procedure of this study was as follows: First, we conducted a separation anxiety test for 400 preschoolers who enrolled in daycare centers and kindergartens at B city and selected three preschoolers who showed high separation anxiety scores as participants with parental consent. Second, we conducted a psychological evaluation. Third, we conducted child-centered play therapy. Fourth, we conducted a separation anxiety test again after terminating therapy. Fifth, we analyzed qualitative data using Yin(2013)’s five-step circulation process and quantitative data using t-test. Results of analyses showed that child-centered play therapy was effective and three preschoolers’ separation anxiety was resolved. This study is meaningful in terms of providing therapists who treat preschoolers who show high separation anxiety with presenting experiential information using various examples of successful therapeutic changes