Abstract: Most qualitative research in sport is based on cases, and the representativeness of cases is always a topic of debate. This study attempts to sort out the methodological basis for case studies to clarify the logical connection between these doctrines of representativeness and the limits of their interpretation. Then it tries to propose a path to dissolve the dilemma of the case's representativeness in sports science. It is found that the representativeness of the case in qualitative research often starts with the "meaning" of the representativeness. Based on the logic of conceptual diffusion of "phenomenon → structure/concept → other phenomena", the representativeness, which is different from that of mathematical statistics, is then established. With reference to the constant comparison method, this study then defines the academic concepts and structural conditions through comparisons between cases with common characteristics, and finally realizes the generalisation of the qualitative research in sports science iteratively.