<p>Incorporating Knowledge Building (KB) pedagogy into reading instruction promotes collaborative inquiry, cognitive engagement, and reading comprehension. While extensive research has explored KB in online settings (e.g., Knowledge Forum), few studies have examined its implementation in offline settings. This study investigates how teacher scaffolding of KB influences student discourse moves and reading comprehension in offline Chinese senior high school EFL reading classrooms. Ten high-quality reading lessons grounded in KB pedagogy were observed, with 1093 teacher utterances and 997 student discourse moves documented. Coding schemes capturing teacher scaffolding, student discourse moves, and levels of reading comprehension were developed iteratively through a data-driven approach. Discourse analysis revealed that among various teacher scaffolding, asking for elaboration was the most frequently used, followed by giving instructions and initiating questions. Correlation analysis and lag sequential analysis showed that specific teacher scaffolding strategies, such as asking for explanations and encouraging participation, significantly influenced student discourse moves, fostering explanatory reasoning, judgment-informed idea integration, and high-level reading comprehension. Nevertheless, the limited occurrence of student-initiated questioning highlighted the sociocultural and educational constraints in the Chinese EFL context. Overall, this study underscores the pedagogical significance of teacher scaffolding of KB in facilitating students’ progressive discourse moves and enhancing their reading comprehension.</p>