本文檢視《安南國譯語》中漢語和越南語的音韻對應關係，觀察所據漢語的韻母現象。發現當時漢語的韻尾*-m併入*-n，*-n、*-ŋ有別；入聲的塞音韻尾消失、產生文白異讀，且宕江、曾梗攝入聲字的文讀音互有區別：宕、江攝文讀音讀圓唇元音，對應越南語o類元音；曾、梗攝入聲字文讀音讀展唇元音，分別對應越南語ɤ類和e類元音。此外唇音字不分開合，蟹、止攝合口來母字介音*-w-消失、並出現*-ej韻母。這些現象皆與現代北京官話非常接近，為漢語音韻史提供了重要的線索。

This paper examines phonological correspondences between finals in Early Mandarin and Vietnamese as reflected in Annanguo Yiyu 安南國譯語. The results can be summarized as follows: the Mandarin final ending *-m had already merged with *-n, but *-n was still distinct from *-ŋ. Entering tone stop endings 入聲 had already disappeared and literary and colloquial readings 文白異讀, representing two distinct phonological strata, emerged. Distinctions were also evident between the literary readings of entering tone characters in the Middle Chinese rhyme classes Dàng 宕攝 and Jiāng 江攝 as compared to those of the Zēng 曾攝 and Gěng 梗攝 rhyme classes; that is, the Dàng and Jiāng rhyme classes had rounded vowels, corresponding to 'o'-type vowels in Vietnamese, while those in the Zēng and Gěng had unrounded vowels, corresponding to '_'-type and 'e'-type vowels in Vietnamese, respectively. Additionally, open 開 and closed 合 rhymes after bilabial initials did not contain any form of distinction. The medial *-w- was dropped after the lateral initial 來母 within the Xiè 蟹攝 and Zhǐ 止攝 rhyme classes, and the final became *-ej. The results of these phenomena are a system of finals that closely resemble Modern Mandarin, or putonghua, and provide important clues for continuing research in the phonological history of Chinese.