This study reviewed the formation, early activities and main members of Dongman Youth League on the basis of records by the Ministry of Foreign Affairs of Japan. The summary follows. First, Dongman Youth League was being formed by a group led by Lee Lin Gu and Lee Ju Hwa from December 1926 and finally was inaugurated in January 1926. The first chairman of the League was Lee Lin Gu. The Dongman Youth League was composed of several departments such as Accounting, Education, Research, Organization, and Youth. Although it may be far-fetched, it seems a youth organization of early socialism Second, its major sub-organizations for youth included Pyong U League, Kando Woman Youth Association. It could be regarded as a massive youth organization including Kukjaga Youth Association, Dong Gu Young Association, Yak Soo Dong Youth Association, in addition to them. Third, a large group of socialists from Shanghais Faction, Hwa Yo Faction, and Bukpunghoi participated in the League and the Chondokyo believers were the mainstream. It seems that when Manju Chongkuk of Hwa Yo Faction was established in June 1926 in Manchuria, Dongman Youth League lost ground. However, as many sub-organizations took fraternization, enhancement of knowledge, and youth physical education as their platforms, it is hard to think they strongly advocated socialism. Fourth, they were committed to propagating socialist ideas through various lectures, book reading clubs, touring library, and distribution or newspapers and pamphlets. In addition, it seemed that they provided education for women by establishing a women's school and were devoted to ideology education for the young generation through a laborers' school. Consequently, it is evaluated that the formation and activities of Dongman Youth League played a positive role in systematically developing Korean communists in Manchuria. Concrete and substantial studies on early communist movement of Koreans in Manchuria are needed.