本文受端木汉语音节结构二分说的启发,认为韵尾的稳固或简约对观察“吴楚方言连续体”具有重要意义,吴湘方言韵母相似性的成因,也许能从湘赣方言的不似找到答案。赣方言的主体韵尾稳固,其西翼及湘方言区则呈现显著的简约性表现。主体赣方言韵尾稳固性的时间深度可推至宋代,而今日湖南人口之绝大部分均为宋以后由江西迁入。从历史音类上看,湘方言韵类的历史深度明显晚于赣方言,与移民史相合;但从共时音系面貌上看,湘赣两大方言的韵尾表现又相差如此悬殊。论文认为,古楚地方言可能是一种韵尾简约型方言,古赣方言入楚之后受其影响,韵尾由稳固变简约,逐步演化为今湘方言及周边湘赣搭界方言。韵尾简约化音变也是造成吴湘方言韵母演变呈现类型学共性的根本原因。 Inspired by the dichotomization of Duanmu Chinese syllables, this paper argues that the stability or simplification of the end of the rhyme is of great importance to the observation of “Wu Chu dialect continuum.” The causes of the similarity of the vowels in Wu Xiang dialect may be deduced from the dialect of Xiang-Gan dialect Find the answer The main body of Gan dialect has a stable ending, and its western wing and Xiang dialect area show a remarkable simplicity. The main body Gan dialect rhyme stability time depth can be pushed to the Song Dynasty, and today the vast majority of Hunan population are moved from Jiangxi after the song. From the perspective of historical phonetics, the historical depth of phonetic class of Xiang dialect is significantly later than that of Gan dialect and coincides with the history of immigration; but from the aspect of synchronic phonetic system, the phonological endings of the two dialects of Hunan and Jiangxi are so different. The dissertation holds that the ancient Chu dialect may be a simple ending dialect, which is influenced by the dialects of ancient Gan and Gan. The ending of the ending of the ancient Hakka dialect is changed from stable to simple, and gradually evolved into the dialect of today in Xiang dialect and the border provinces of Hunan and Jiangxi. Conclusive phonetic changes are also the root causes of the common typology of Wu Xiang dialect vowels evolution.