Objectives The purposes of this study were to explore the understanding of the Nuri Curriculum and experiences in the curriculum integration activities in the play-centered teaching demonstration of pre-service early childhood teachers. Methods The participants in this study were 20 pre-service early childhood teachers who attended early childhood teacher education courses at K University in Gyeonggi. The research data were collected three times and qualitatively analyzed the reflective journals on the experiences while performing play-centered activities in connection with the Nuri course in the teaching demonstration process. Results The results of the study are that first, pre-service early childhood teachers tried to understand the Nuri Curriculum for early childhood play-centered classes, to integrate it with the subject, and to find the educational meaning. Second, it was found that pre-service early childhood teachers, as supporters of early childhood play, organize and implement activities in the course of teaching demonstrations, develop reflective thinking skills, and improve their professionalism as cooperators for child-led play support. Conclusions Based on the results of this study, it was discussed how to improve the understanding of the Nuri Curriculum and the professionalism of the integrated curriculum.