The Southern Song dynasty marks the beginning of Chinese study on the marginalia of ancient proses. It was then when "crucial" literary theory and terms were established to analyze the structure and coherence of writings. This paper analyzes the theory established since the Six Dynasties in regard to tishi and qishi , as well as their related critical terms, and finds that "crucial" literary theory for the marginalia in ancient proses in fact combine "wenfa" and "wenshi", two concepts that are closely intertwined. Tishi focuses on the construction and layout of the whole piece of writing, while qishi emphasizes the forms of individual sentences. To put these two together allows one to better understand the characteristics of ancient marginalia criticism, and to discover the aesthetics of ancient proses, which is full of twists and turns, as well as powerful rhythm.