The main purpose of the study is to research influences on the principal¡¦s leadership and the school effectiveness of the principal-selecting system of elementary schools in Kaohsiung City. The study is divided into three sections. The first issue is focused not only on investigating the fundamental theories about the principal-selecting systems, leadership and the school effectiveness, but also on analyzing some related empirical researches. Second, the efforts are concentrated on finding out the current status and the variation of the principal¡¦s leadership and the school effectiveness. Therefore, we will realize the changes and examine the correlations among the two variables and the principal-selecting system. Finally, the concrete conclusions combined with records and results of my research will be devoted to consider about improving the school effectiveness and the principal¡¦s leadership. The approach is the Questionnaire-method with stratified sampling randomly. Based on the results from studied reports and recommendations from experts in this field, an analyzing tool with high reliabilities has been developed, titled ¡§A questionnaire for exploring the influences of existing principal-selecting system on the principle¡¦s leadership style and the school effectiveness.¡¨ A total of 600 teachers from 86 elementary schools responded the questionnaire, in a population of 36 public elementary schools in Kaohsiung City. Of them, 466 valid copies, approximately 97%, are collected. Data was analyzed with computers by traditional or state-of- the-art statistic methods, such as Arithmetic Mean, Standard Deviation, T-test, One-way ANOVA, and Pearson Product-moment Correlation. Main findings obtained from the study are as follows: 1. The elementary principle¡¦s leadership style approximately is conformed with the transformational and transactional leadership as the principal-selecting system have been brought into force. 2. Teachers realize the principle¡¦s leadership style from many views because of differences among their educational background, sex, and function. 3. After taking the principal-selecting system effect, the elementary principle¡¦s leadership style and the school effectiveness are improving. 4. Therefore, the quality of teaching is improving better than other parts of the school effectiveness. 5. Besides, teachers respectively recognize the school effectiveness through some different basic variables. 6. In conclusion, the principle¡¦s leadership style is related positively to the school effectiveness. According to analysis of records and results of researches, the above-mentioned issues will be suggested for concern to the educational administrators, the elementary principles, and correlative researchers in the future.