This paper aims to examine the bibliography and composition of Dongmun yuhae, and methods of writing Manchu words in Hangeul in Dongmun yuhae published in 1748. The Manchu language was generally written in their own letter, but sometimes in other scripts. Dongmun yuhae is the earliest book among the extant manchu ones in which the Manchu language is written in Hangeul. In this paper, I examined the bibliographical characteristics and composition of this book in the first. And I analysed Manchu words and methods of writing them in Hangeul, based on the forms in Manchu dictionaries which were published earlier than Dongmun yuhae. As a result, it was found out that almost all the Manchu words in the book had their sources from early Manchu dictionaries, and for the accuracy, the Korean letter is used with diacritic marks in sophisticated manner.