China is at the crucial period of modernization and more talents with high level of modernity are needed. In China's modernization process, western China is believed to the most difficult place as well as the niche point. Among all the factors affecting people's modernity development, school education is the most important. Students in compulsory schools are at the critical development period of their thoughts, ideas, attitudes and behaviors. Two thirds of their mental awakening time is spent in schools, and they are affected imperceptibly by their significant others in schools, including the principals and the teacher. A principal is the spiritual leader of a school, and his or her thought and ideological orientation reflected by their leadership styles affect the development of students' modernity.However, in the past studies, there were no conclusions regarding which leadership styles had more impact on students' modernity development. Using the cluster random sampling, this study investigated 378 teachers in 50 compulsory education schools from the provinces of Yunnan, Guizhou, Xinjiang, Guangxi and the city of Chongqing. All the variables were measured by teachers, including transformational leadership, transactional leadership, and students' modernity, as teachers are the intermediate actors between principals and students. Teachers are the best appraisers of principal leadership, as principal's cognitive behavior is directly shown in their leading process, which can be felt firsthand by teachers. Also teachers are closer to their students and familiar with their level of modernity. The data was collected and analyzed by the software of SPSS20.0 and AMOS20.0.The findings showed that both transformational leadership and its dimensions (r were between 0.373 and 0.579), transactional leadership and its dimensions (r were between 0.239 and 0.478) had significant relationships with students' modernity, but transformational leadership had closer ones. All the four dimensions of transformational leaderships, such as idealized influence (β=0.164, p < 0.05), inspirational motivation (β=0.253, p < 0.01), intellectual stimulation (β=0.159, p < 0.05), and individualized consideration (β=0.164, p < 0.05), had significant effects on students' modernity, all of which can explain 42.0% of the change in students' modernity. The two dimensions of transactional leadership, contingency motivation (β=0.388, p < 0.001) and exception management (β=0.185, p < 0.01) also had significant effects on students' modernity, both of which can explain 26.6% of the change in students' modernity. When the impact of transactional leadership was controlled, transformational leadership had significant and exceptional impact on students' modernity and all its dimensions. However, when the impact of transformational leadership was controlled, transactional leadership had no or less significant impact on students' modernity or its dimensions. These results showed that transformational leadership had more advantage than transactional leadership on affecting students' modernity.Based on the findings, it's suggested that principals should change their leadership styles, and strengthen their consciousness and transformational leadership in support of the development of students' modernity.