This study aims to explore how principals of K12 private schools in China practice transformational leadership and focuses on schools in the Sichuan-Chongqing region. The study focuses on five dimensions of transformational leadership: setting direction, developing people, redesigning the organization, improving instructional program and related practices. To gain insights into the specific performance of these dimensions, the study adopts qualitative research, combined with case studies, and collected data through observations, semistructured interviews, and document analysis. The findings reveal 15 specific practices under the five dimensions that provide important support for school development. By analyzing the practices of principals in Chinese K12 private schools, fills a gap in research on the application of transformational leadership in private K12 education in China, and provide new perspectives to deepen the theoretical content. Based on the uniqueness of the Chinese educational context, the findings of this study firstly support the culturally adaptive and contextualized application of transformational leadership theory. Second, the study provides concrete transformational leadership practices for Chinese K12 private school principals to help them drive school reform and development more effectively. Finally, the study highlights the typicality of the special education context and sample selection in the Sichuan-Chongqing region, which provides a reference for educational reform in similar contexts. The novelty of this study lies in revealing the specific practices of the five dimensions of transformational leadership and demonstrating how they can support sustainable school development, as well as providing actionable recommendations for private principals.