Effective teacher discourse is critical in improving English as a foreign language (EFL) education, particularly in junior high schools in China, where students are at a crucial stage in their language development. As junior high school students are at a pivotal developmental stage, this research investigates the discourse patterns employed by novice and expert teachers to assess their impact on students' engagement and language acquisition. Despite the extensive research on teacher discourse in higher education, a significant gap remains regarding its application in compulsory primary education settings. This study aims to fill this gap by examining the current classroom discourse patterns of EFL teachers in junior high schools to identify the distinctions between novice and expert teachers and explore the factors contributing to these differences. This mixed-methods study includes qualitative and quantitative analyses. Verbatim transcriptions of six classes were used to create a corpus exceeding 20,000 words. The data were analysed using cross-tabulation in Excel and Chi-square tests in SPSS 22.0, complemented by semi-structured interviews with selected teachers. The theoretical framework is grounded in Long's（1996）interaction hypothesis, which underlines the significance of communication in facilitating language proficiency through meaningful interaction, and the analysis follows Sinclair and Coulthard's（1975）discourse patterns. The initiation-response-feedback (IRF) and initiation-response-0 (IR0) emerged as predominant patterns among both novice and expert teachers. Novice teachers predominantly relied on the basic IRF pattern, while expert teachers exhibited greater flexibility and more frequent use of variant patterns, such as IRFR, I[RnFn] and [InRn]F. Such adaptability among expert teachers creates a more interactive and engaging learning environment, thereby enhancing student participation and language acquisition. The study also identifies a novel variant structure, IRnF, used more frequently by expert teachers, underlining the benefits of group work in fostering teamwork and independent thinking. Expert teachers demonstrated a greater propensity to adapt their discourse strategies to foster a more production-oriented learning environment, which was the main factor driving the teachers' differing discourse patterns. This study significantly contributes to the analysis of teacher discourse in the junior high school EFL context, providing empirical evidence and practical insights that bridge the gap between theory and practice. By elucidating the distinct discourse practices of novice and expert teachers, this study offers valuable recommendations for teacher professional development and highlights the importance of employing varied and interactive discourse structures to improve EFL teaching effectiveness. The study also provides valuable insights for educators striving to improve their instructional practices and the language acquisition in EFL classrooms.