Rhyme books and rhyme tables are the most important resources on the study of Ancient Chinese, especially in rhyme books such as Chie Yun (切韻) and the early rhyme tables --Yun Jing (韻鏡) and Chi Yin Liue (七音略). The format of division rhyme table is a supplement to rhyme book which is characterized by the verbalization in rime. Rhyme tables expose the shortcoming of unclear syllable structures, indicate the errors in Fan Chie (反切), and reflect the phonological changes from Archaic Chinese to Ancient Chinese. In addition to the interlaced arrangement of “sound-incolumn and rhyme-in-row”, a rhyme table is particular about distinction of “kai-he divisions”(開合等第), which highlight the phoneme of medials. In a rhyme table, open vowels and close vowels are mostly charted in separate tables. The division medials, on the other hand, are grouped by four tones into four grades (i.e., divisions). Either of them is presented in different way of tabulation. From the perspective of “hsieh-sheng” (諧聲) system, rhymes in different divisions can be hsieh-sheng mutually. However, rhymes either with an open vowel or a closed vowel are hsieh-sheng separately. Fang-Kuei Li (1971) stated, “division initials such as見k-、溪kh-、群g-、曉x-、匣ɣ-、影 · - in Ancient Chinese can be hsieh-sheng mutually in most cases, though rimes in open mouth are hsieh-sheng in one group and those in closed mouth are another… vowels in the first and the second divisions are hsieh-sheng with the third one… the closed-mouth medials seem to differ from medials in the third division and should be considered as initials.” Yakhontov and Pulleyblank believed that closed-mouth medials in Ancient Chinese were generated in the later period. This article explores the phonology of closed mouth syllables in Archaic Chinese, retraces systematically and demonstrates the closed mouth syllables as products in the later period.