The purpose of this article is to analyze how North Korea has studied about the operations and establishment of the Republic of Korea (ROK) military defense system on the basis of research data and DB collected at home and abroad. To do it, this paper used a wide range of regular or irregular periodicals and books on research on the ROK made by North Korea, which have held at home and abroad up to now since the North Korean regimes were established in 1948. Subsequently, this research paper abstracted research literature data in which covered only the ROK military affairs out of data on the ROK collected by North Korea. It was 12 out of 37 magazines that were selected as research data. Accordingly, this research paper made the analysis on how North Korea approached the ROK military affairs. First of all, Namjoseonmunje (Issues about the ROK) was mainly covered in regular periodicals, which the North published. Given the research on the ROK military affairs made by the North Korean regimes, it is evidenced that researches on the US military affairs were made more intensively than the ROK counterpart. Also, a majority of critical researches on the US and ROK military alliance have been made. It is so because researches on the the ROK military affairs made by North Korea have put the focal points on the ROK which is militarily subordinate to the US. It was the mid and end of the 1960s that the North Korean Government began to research the ROK military affairs. Most researches on the ROK military affairs conducted by North Korea were of the government regimes of the late Park Jung-hee' military education and military policy critics, during the 1960s and 70s. In the 1980s when the military regimes were still governed in the ROK, issues on the criticisms for the Jun Doo-hwan regime and the ROK military affairs were dealt with. The periods of the 1980s witnessed very active the ROK military researches made in the North. This results from the US and the ROK military alliance operations and training, that took place in 1976, and in more details, from the strong resistance by the North against the Team Spirit and propaganda of it as national solidarity. One of the marked research traits that North has dealt with the ROK military realms is what North Korea sees the the ROK military as military colonized under the US troops, and is what the the ROK military spheres have been at issues in multi-lights. And, the North Korean regimes continues to study the ROK military system to rationalize the North Korean regimes and propagate such regime to North Korean people. Strictly speaking, the research intention of the North to regard the ROK as Military colonized under the US troops differs from what has already been known. In other ways, the North Korean regimes make the research on it merely to propagate North Korean people about North Korea.