This study aims to review the overall characteristics of the local defense system in the early Koryo dynasty. It can be summarized that it was grounded on the regional community defense systems. I also found out that such regional community defense system did not operate itself but perform its role in the context of local defense system in Koryo dynasty. From the perspective of local defense system, the Koryo was dependent on the community self-defense capability of each region. Thus, each Kunhyun(郡縣) meant to be the unit of defense system. Koryo people in each Kunhyun had been able to defend themselves centering on the local castle as the center of their administrative control. It can be maintained that the Mongol invasion marked a turning point in the manner of such a local defense system of Koryo dynasty.