漢語上古音系的研究起源甚早，自宋朝吳棫開始爰及清朝終於使得古韻的研究達到了歷史的高峰，尤其「審音派」的清儒已能運用一些等價於現代結構主義的語言學理論，在語言理論研究的起跑點上，實遠超於西方具現代意義的語言學理論。「語言」是成系統的結構體，古音的研究若能慮及「結構」、「系統」、「成分」與「關係」等諸多面向的問題，無疑能為漢語的古音研究帶出更具語言學意義的成績。筆者透過「音韻格局」的考察，指出李方桂先生的古音系統中尚有許多的結構空檔需進一步的解釋與說明，準此，本文論題的側重點便在於檢討上古「祭、月」兩部的分劃與否，操作程序上利用結構主義的語言學理論，重新查考韻部間的元音分布及與韻尾的組合關係，並配合果攝去聲中諧聲偏旁的上古來源分析等幾重思考，認為漢語上古音系「祭、月」兩部合一為宜。

Research of phonology origins of Old Chinese is early. The research from Wu-Yu(吳棫) until Qing dynasty, they make the research reached a historic peak, especially ”Pronunciation” has been able to use some modern linguistic theory of the Structuralism. ”Language” is a system of structures, if the research of Old Chinese phonology takes ”structure” and ”system” and ”composition” and ”relationship” questions, no doubt for the research of Old Chinese phonology with a more linguistic significance of the results. The writer through ”phonology pattern” of investigation, pointed out that that the Old Chinese pronunciation system of Li Fang-gui(李方桂) has many of structure free needed to explain. This article is focused on ”jì(祭)and yuè(月)” of Old Chinese rhyme categories, use the linguistic theory of the Structuralism, review the distribution of vowels and the combination relationship of syllable coda, and analysis Ancient sources of ”guǒ”(果)group's falling tone. The writer think ”jì(祭)and yuè(月)” of Old Chinese rhyme categories should be one.