Guangxi is a border area where ethnic minorities are distributed, with poor economic development foundation, slow growth, relatively traditional, high turnover rate and outdated education. The purpose of the study was to evaluate the impact and to identify the path of principals' transformational leadership on teachers' teaching effectiveness in ethnic autonomous region of China. A regression analysis survey design was adopted to collect the data from the teachers of elementary schools. Based on 5-point Likert Scale of 771 questionnaires from Guangxi Province of China, the survey concluded: (1) principals' transformational leadership, teachers' organizational commitment, and teachers' teaching effectiveness differed significantly by gender and age, (2) principals' transformational leadership significantly influenced teachers' teaching effectiveness, in addition, teachers' organization commitment can partially mediate the effects, (3) gender can moderate the path of principals' transformational leadership to teachers' organization commitment, specifically, male teachers carry more weight. The study findings may serve as a guide for further research on management and leadership of leaders and members in educational organizations.