This study considers the characteristics of the separation of public and private security service during Koryo dynasty, and compares it with the modern security service. Modern day security serviceʼs definition of private and public security service was used to distinguish them. Given the different historical settings, itʼs difficult to argue that the distinction between public and private service during Koryo dynasty was clear, but it can be said that public security service was centered around palace guard and concerns the activities of protest, and military made for the relationship, and private security service was centered around power of DoBang and includes the activities of malingering, and Byolchogun. During the early days of Koryo, protest, district military and soldiers who stay in the palace were all parts of a palace revolt and this institutional improvement of soldiers who stay in the palace was accomplished during King Seongjongʼs rule. The tradition of a palace revolt can find its roots in the middle military, and after the unification, a palace revolt was reformed into the king's palace revolt of second and the 6th along the course of establishing the nationʼs system. All of the changes stem from the reformation for consolidating the royal authority. Gyung Dae Seoung wanted to protect himself and he slept with his army night and days and because of that, group of soldiers was created and it was called DOBANG. Some members were from dobang gyeonryong, The forced were powerful because it was gathered with a warriors with extraordinaire martial arts and competent management. Most of the soldiers followed gyeong dae seung because they believed that he has a strong leadership and loves his people, and had a strong faith in him. However, the general gyeong jang had a belief that politics must be reverted to the previous so the relationships between jungbang wasn't smooth. Because of the economic operational problems, due to fraud committed by the mens under his command failed to maintain integrity and was criticised.The misconception also fed up with the emperor and the deepening relationships between the soldiers, his dobang was dismantled. After he took over the dobang, for his personal safety and to strengthen his position he compensated gyeon dae seong's dobang and developed the organization. In the process of extending the dobang Choi chung heon recruited many talented people to strengthen the military base, and also accepted the advice and expanded the power of Dobang. Choi Chung Heon thus consolidated his political gains by weakening the power of the king's army and adjusting the myth, which could've threatened his regime, and this was called Dobang number 6th. Dobang number six got even more powerful by his son named Choi woo, and after ruling, he expanded into a room, and a substantial reorganization of Dobang was developed. And then the creation of yabyeolcho also showed the effect to prevent the crisis. Although the palace guards who were public security service of Koryo Dynasty was still maintained during the military rule era when the royal authority was incapacitated, it was only maintained to have a symbolic meaning as the actual authority including military power was with Choi, the master of Dobang, private security service group. Likewise, during the rule of Choi, private securty service could reign over public security service, and the noteworthy characteristic of Dobang is that it assisted the private soldier groups to seize the military power by reorganizing and modifying military system. Although both differences and similarities can be found when comparing the guards of Koryo Dynasty with those of contemporary society, they have a similarity in terms of the essence of guards that they guarantee the safety of their clients. As for differences, the royalty of Koryo Dynasty and the pursuit of profit of contemporary society are in contrast, and contemporary guards can be seen as the fulfillment of responsibility and duty by free will, whereas guards of Koryo Dynasty were ruled with military coercion.