Abstract: In the “Preface to the Twenty Chapters of ‘Zhuanyu’”,DAI Zhen took function words as examples, followed two connection standards of the meaning and archaic Chinese pronunciation, and adopted the parallel mutual corroboration method to prove “weitong”, one type of the time-place phonological change in the ancient times with evolved pronunciation position but unchanged pronunciation method. On the premise of “yitong(synonymy)”, the parallel mutual corroboration method can be used to verify relations between cognate words which have undergone regular pronunciation change in ancient, and the glyphs also have been correspondingly different. DAI Zhen's parallel mutual corroboration method is scientific and rigorous. It has multi-level logic from surface to inside. In this study, DAI Zhen's method is adopted to analyze the nine groups of commonly used function words and to discuss the etymology and pronunciation conversion types. It is found that the conversion on initials includes the interconversion of Ni-Xia, Ni-Yu and Xia/Yi-Yu, while the conversion on finals includes the interconversion of Yu-Zhi, Ge-Yu, and Ge-Yu-Zhi.

Key words: DAI Zhen, weitong, etymology, archaic Chinese, zhuanyu, function word