自先秦《詩經》成了四言體裁集大成作品之後，討論者眾，繁華過盡，後世以四言體裁為研究對象者遂寡，使得四言體裁成為詩歌學術討論相對較缺乏關愛之一環，甚為可惜。晉代摯虞與梁代劉勰不約而同界定四言體裁詩歌為「正體」，正體與四言詩的關係，在先秦《詩‧大序》僅約略可見「正」與「變」的對舉，在漢代以前則呈現正變不明的情況，四言體詩歌可以說是到了摯虞才正式被稱為「正體」。究竟四言體詩歌有何特殊風格與地位？詩論家何以將之標舉為「正體」？而此一「正體」說法，對於魏晉時期的四言詩又有什麼影響？本文透過南朝以前的詩歌論述與詩歌流變，進行詳細且深入的探討。 四言詩歌在魏晉時期與五言詩歌同時並存，其間的消長遂成為當時詩歌流變的脈絡。本文參酌以五言詩為對象進行之討論與其建立的魏晉時期五言詩歌譜系，透過對魏晉時期四言詩脈絡進行詳細歸納整理，並且藉由對四言詩歌作品完整且細密的分類，以嚴謹架構出當時四言詩歌的內在質素。此外，從類型由來與區分的探究中，進一步剖析四言詩之所以被形塑為「正體」依據的緣由，以深入探勘魏晉時期所闕漏的四言詩歌討論，希冀確立四言詩在詩歌史之定位。本研究並在四言詩歌類型的篩選與討論上，透過量化分析方式，藉由創作類型比例的高低作為另一客觀的討論基礎，同時依憑數據化的討論，揭示、呈現四言詩歌在魏晉時期完整且確然的狀態。 / In Jin and Liang Dynasties, Zhi Yu (摯虞) and Liu Xie (劉勰) both defined four-word poetry as " Zheng Ti" (Classical Form). Actually, the form of four-word poetry was called "Zheng Ti" until Zhi Yu. Why those critics called the four-word poetry with classical form? What could we figure out the special type and cultural level of "Zheng Ti"? And the thought of classical form compared what kind of imagination in the four-word poetry during Wei and Jin Dynasties? In this paper, the reasons why four-word poetry associated with "Zheng Ti" were discovered through the Southern Dynasties poetry discussion with variation in prosody. The four-word and five-word poetry both coexist in the Wei and Jin Dynasties. The growth and decline between the two forms composed of the poetry changed at that time. In this paper, the four-word poetry classifications system was established and the qualities were found through the researches about five-word poetry classifications and the system of five-word poetry in Wei and Jin Dynasties. Besides, the research through screening and discussion of four-word poetry, based on quantitative analysis, the proportion of every type in the classifications system from high to low could be an objective basis for discussion. Relied upon a discussion of the data, this paper will render the complete and mature condition of four-word poetry, and fill up the lake of discussion in four-word poetry history of positioning in Wei and Jin Dynasties.