本研究旨在探討三位國小英語教師的專業知識及其課堂教學，並分析影響其知識及教學的因素。透過個案研究的方式，本研究呈現了國小英語教師的課堂教學，其中探討了其教學如何受教學專業知識的影響並探索了形成教學專業知識的來源。 本研究採取質性的研究方法，研究過程採取訪談，教學觀察，文件分析等主要資料蒐集來源，為期約兩個月。資料的涵蓋層面包括：(1)班級經營 (2) 課程教學 (3) 形成知識的來源。經由這些資料，本研究討論了三位教師專業知識的異同：(1) 各個教師對自己的教學觀點如何 (2) 各個教師如何受其工作場域的影響 (3)各個教師的知識來源如何形成。 本研究根據以上議題的討論結果，進一步提供相關建議，以期能作為英語師資培育人員，英語教師及未來研究的參考。 / The purpose of the study was to investigate the professional knowledge and its influence on classroom practices of elementary school English teachers. Cross cases analysis was conducted to examine the differences and similarities of three subject teachers concerning their professional knowledge, classroom practices and derived sources of knowledge. Qualitative approach was adopted to look into the professional knowledge of three elementary school English teachers in Taipei. The data was collected through interviews, classroom observations, and document analysis. In this study, the knowledge of three teachers was presented in the following areas: (1) classroom management, (2) enactment of curriculum (3) sources of teacher’s knowledge. Based on the above information, this study discussed the qualitative differences of knowledge of three teachers under two dimensions: (1) how the teachers perceived their teaching (2) how the teachers responded to their working contexts. As for sources of teacher’s knowledge, three factors were discussed: (1) learning experiences (2) teaching experiences (3) contextual factors. Finally, pedagogical implications and suggestions based on the study results are presented mainly for teacher educators and English teachers.