The study investigated the thinking styles and their Relevant variables of junior high school principals on the basis of R. J. Sternberg’s theory of mental self-government, and further explored the similarities of thinking styles between principals and deans, the consistency and inconsistency in terms of satisfaction between principals and teachers, and the correlation between thinking styles and leadership styles of principals. Subjects include 199 principals of 306 junior high schools in Taiwan, and 45 principals, 142 deans and 261 teachers of Kaohsiung’s and Pington’s junior high schools in Taiwan. Data were measured through TSQ, LSQ, DTSQ, TSQT, and LPSC, and were analyzed with Frequency t-test, chi-square test, Pearson’s product-moment correlation, and two-way ANOVA. Results indicated 1) thinking styles of junior high schools principals in Taiwan are more executive on Function; more hierarchy on Form; more global on Level; more external on Scope; more liberal on Leaning, 2) principles will choose teachers of executive thinking style as deans, and 3) teachers of similar thinking style to that of principals will give more credit to principals’ leadership. In sum, this study basically supports some of Sternberg’s concepts in his theory of mental self-government.