Most research suggests professional development improves teachers' knowledge and pedagogy and enhances teachers' confidence to facilitate a positive attitude about student learning. This study attempted to investigate the connection between teacher professional development program and students' Learning. This study took Readers' Theater Teaching Program (RTTP) for professional development as an example to inquiry how participants applied their new knowledge and skills learned from RTTP to their teaching practice and how the impact influenced students' reading fluency. This study was a two-year project. In the first year, this study focused on designing and implementing RTTP and evaluating participants' satisfaction of RTTP, what they learned and how they applied it to design their English reading curriculum. In the second year, the study adopted quasi-experimental design approach and evaluated how participants RT instruction influenced their students' reading fluency. The participants in this study composed two junior high school English teachers and their students. Data was collected from a number of different sources including teaching observation, semi-structured interviews, teaching diary, teachers' professional development portfolio, pre/post RT content knowledge tests, teacher survey, and students' reading fluency tests. The results indicated that teachers learned more RT script writing than other specific contents and hold a positive attitude toward RT instruction and considered it as a very wonderful strategy to meet a variety of needs. All of the experimental group students had a big progress in reading fluency after RT instruction. The evidences from this study indicated that RT English instruction significantly influenced students' reading fluency and classroom climate.