Although Chinese early childhood education policies have high expectations for kindergarten teachers' play pedagogy, teaching and play are still discussed as a bifurcation in Chinese kindergartens' daily practice. To support Chinese kindergarten teachers' development of play pedagogy, this study conducted an educational experiment (EE) framed by cultural-historical theory. The study was conducted in a public kindergarten located in the northeast of China. Two teachers and 34 children (4-5 years) were involved in the study. The data were collected using the methods of digital video observation, interviews, and focus group discussions. The findings indicate that EE creates a new social situation that can motivate teachers' development in ways of collaborative teaching. Moreover, the collective reflection and Conceptual PlayWorld (CPW) implementation within the EE amplified teachers' play pedagogy development. We argue that the EE works as a source of teachers' professional development (PD) and builds their identity as experts in creating playful learning environments in a Chinese cultural context.