Preschool curriculum reform is currently underway in Taiwan. Privately-managed public preschools (PMPPs) currently play the role of bellwethers because they stand halfway between public and private preschools, and serve as testing grounds for curriculum reforms promoted by the government. This study originated from Curriculum Development Program (CDP) which is one of Taiwan government's policies toward PMPPs. The researcher and the research subject consisted of the expert and case school participating in this program. The main objective of this article was to discuss the course about a privately-managed public preschool how to overcome difficulties and establish a process pattern of CDP. This paper employed the qualitative research methods; it included focus group, interviews, and action research. Then, the study made use of grounded theory and conducted data analysis in the three stages of open coding, axial coding, and selective coding. Based on the results of this study, the CDP exerted a mediating effect that harmonized the tensions between external impact and internal resistance. The difficulties for the external impact of CDP included: educational policy reforms, competition in the education market, and parents' right to choose. The internal resistance of CDP included: changes in the curriculum power structure, limitations on in-school resources, and conflicts of interest among organization members. The process pattern included: use of curriculum guidance experts and action research; integration of interested parties' resources and organization of a specialist curriculum development team; responding to internal and external needs by establishing a compromise between school-based curriculum vision and assessment approach; harmonizing external impacts and internal resistance to complete the school-based curriculum; and cyclic reflection on and revision of action plan. This study provided practical insights and offered an integrated solution of how an assistance approach with experts' participation can be combined with curriculum policy and academic research.