This set of 6 books which is the first book about standard pronunciation was written by the scholars such as Sukju Sin, Hang Choi and Paengnyeon Park at the behest of the king and was published in the 30th year of King Sejong, Chosun Kingdom (1448). It compares to the "Hongmoojeongwoon" which is a book about pronunciation in China, and "Donggukjeongun" means "correct pronunciation of Korea (East Country)." It was written and published to correct the pronunciation of chinese characters and to set standard pronunciation which were confused by many. Larger letters of the main text were printed with wooden types, while smaller ones were printed with Gapinja and the preface was printed with larger Gapinja. Books are measured 19.8 cm wide and 31.9 cm long. The set is made of 7 pages of preface, 4 pages of table of contents, 46 pages of the first volume, 47 pages of the second, 46 pages of the third, 40 pages of the fourth, 43 pages of the fifth and 44 pages of the sixth. When it is compared to the other Donggukjeonun (National Treasure No.71) which was printed simultaneously, there are following differences. First, its top and bottom margins of the pages were cut off slightly during re-binding. Second, both have titles printed with wooden types, however they have different styles of type. The order of books is hand written as Ye, Ak, Sa, Eo, Seo, and Su which presumably were added later. These books have a significant meaning because the pronunciation of chinese characters were written for the first time, and its importance as a research data of Korean linguistics is evaluated as important as Hoonminjeongum. Not only in phonological study of Chinese but also in the background of creating characters in Hoonminjeongum and phonological study, they are used as fundamental references. This set of book, along with Donggukjeonun, (National Treasure No.71), holds enormous value for phonologic study.