The purpose of this study was to investigate the differences through a comparison of the police system in North and South Korea and find its integration measures to prepare for the unification of North and South Korea. For the purpose, this study examined closely the meaning and necessity of unification and police system to prepare for the unification of North and South Korea. After that, this study investigated the differences shown in the transformation process of police system through a comparison of the police system in North and South Korea and derived its integration measures to prepare for the unification of North and South Korea. The results of this study are as followed. The police system of North and South Korea showed serious differences in organizational structure, rank, selection, and promotion of police officer, etc.. Therefore, a lot of effort turned out to be necessary in the process of preparation for unification of North and South Korea. First, the supreme unifying principle for police system of North and South Korea must be emphasized the principle of efficiency internally, the principle of autonomy and democracy externally. Second, the integration of police system to prepare for the unification of North and South Korea should be done stage by stage such as preparation phase, implementation phase and completion phase.