This chapter presents the methodological framework for investigating the implementation of Assessment for Learning (AfL) in Chinese university English-as-a-foreign-language classrooms. Focusing specifically on the research design, it details a two-phase, mixed-methods approach to examine both teacher and student perspectives. The chapter first outlines the quantitative phase, including the development and validation of questionnaires for teachers and students, sampling strategies, and data analysis procedures. Next, it describes the qualitative phase, explaining the selection criteria for case studies, data collection methods, and the thematic analysis approach. Special emphasis is placed on how these methodological choices address the study’s dual objectives: (1) evaluating the perceived value and practical implementation of AfL strategies, and (2) identifying contextual factors influencing their adoption. By systematically documenting this framework, the chapter establishes a robust foundation for interpreting findings about AfL’s role in China’s unique educational context.