『Hunminjeongumunhaegns(訓民正音韻解)』, and so on what is known the book’s name so far as that revealed by the new 『Jeojeongseo(低井書)』. It has confirmed that this book, well known for its different names, that is, 『Hunminjeongeum Dohae』, 『Hunminjeongeum Unhae』, 『Unhae Hunminjeongeum』, and so on, is a bound one 『Jeojeongseo』, in which 『Unseo』 is bound with 『Gaehapsajang』(both are transcribed versions) in this article. It is therefore an inevitable step for us to change the title of this book. The book 『Jejeongseo』 consists of two main parts. The one part is named as “Unhae” which covers from to , and the other part is named as “Gaehapsajang” which is composed of Undo(the table for arranging Chinese characters). It has certified that we can call this book 『Jeojeongseo』 only when these two parts combine together by discovering the research materials. Yeoam Shin Gyeong-jun, the author of 『Jeojeongseo』, was a practical theorist for the Chinese phonology, he learned the Chinese phonology from his master, Choi Seok-jeong and it is supposed that he visited him and learned it when his master, Byeongwa, had dwelling in Ganghwado Island. And from the fact that Shin Gyeong-jun wrote 『Samungwoljahwi』 in order to add the omitted words in 『Samunseonghwi』 written by Hong Gye-heui, they were in an interactional relationship. It is assumed that Yeoam Shin Gyeong-jun intended to make an ideal table for the sounds of Sino-Korean characters by making use of Hunminjeongeum and at the same time he wanted to make a suitable dictionary for his table, Undo 『Gaehapsajang』 with the complement to missing words in ‘Samunseonghwi’ in that he wrote the book 『Samungwoljahwi』. Most of researchers lacked understanding on its organization, they called the latter part ‘the phonological table for Chinese characters(漢字音韻圖)’ before the discovery of the manuscript of 『Jeojeongseo』. This term is not entirely wrong but the process of unity of term should be to work because the term ‘Gaehapsajang’ is specified in the discovered book. Along with 『Unseo』, 『Gaehapsajang』 is one of the key parts of the book 『Jeojeongseo』. In the front part of it, as being based on tables for arranging Chinese characters in <『Gwangun』36 alphabets>, <『Unhoe』 35 alphabets>, and 『Saseongtonghae』, it cites intactly Choi Se-jin’s annotations. It represents the sounds of SinoKorean characters in an alphabetical structure according to the way of arrangement for the latter parts of syllables of the Chinese language(Unmo) except for newly arranging lingual sounds in the tables for arranging Chinese characters of 『Hongmujeongun』 in his own way. Eventually, Shin Gyeong-jun recognized the structure which is made up of 36 seongmo(the initial consonants of syllables of the Chinese language) and 18 unmo(the latter sounds of syllables of the Chinese language) as a phonological system.