After the liberation of Korea, there were diverse scholars with different historical view points. While they summarized and accepted the research results during the Japanese colonial rule and comprehensively reviewed cultural history, social and economic history and pragmatic history, they also sought proper historical research methodology for the new ear. Lee Neung Sik, subject figure to this study, was one of those who attempted such. He was the pioneering figure to liberate our history from the colonial historical perspective and to set own historical theory in the midst of mixed and conflict historical view points. He was also an excellent history educator to imbue students national consciousness and to teach historic methodology systematically. This study attempted to figure out his position and meaning in our history by summarizing his life that was totally disregarded for his defect to North Korea. Based on the statement by his students in Gyeongbuk Middle School and Department of History Education of Seoul National University, he was forced to defect to North Korea. And this study also found out that while he was favorable to materialism he attempted to arrange the ideological chaos in the historical society in Korea after the liberation by seeking the harmony between social economical history and practical history.