Abstract: What characterized the early development of sociology in modern China was its emphasis on the firsthand research of Chinese society. Among those who carried out works of this kind, LI Jinghan's contributions were indeed distinguished. In his writings, he articulated the significant role that the science-based social research would play for the modernization of China. While he pioneered to conduct social survey among the urban poor and peasant population, he and his collaborators made tremendous efforts to address the resistance from his subjects due to the given cultural and political traditions. LI can be considered very fortunate to have been able to participate in the renowned rural reconstruction experiment in the Ding County in northern China, where he and his teammates left important legacies in the application of science to social reform and social progress in China at that time. The paper also critically assesses the methodological limitations of his works, e.g. his overemphasis on scientific idealism, sampling issues, and research ethics.