Understanding of unification between South and North Korea is totally different. While South Korea defines unification as a process for the formation of new national community, North Korea considers it building a proletarian class society on the whole Korean Peninsula by national liberation and revolution of South Chosen(South Korea). Due to this different perception, considerable discrepancies are to be inevitably shown in the basis and principles(or their interpretation) of unification policies between the two Koreas. Especially, the South and the North conflict in unification philosophy because the former pursues free and democratic unification and the latter aims at unification by "Juche" ideology. The same is true with South and North Korea's unification formulas, namely "Korean National Community Unification Formula" and "Democratic Confederal(this term is used to mean "federal" and bring about much confusion among Korean people) Republic of Koryo", which include key elements and general features of their unification policies. As is well-known, North Korea suggested so-called "Low Level of Federation" Idea in 1991. From that time on, it seems that there are some similarity between the South's "Korean Commonwealth" idea and the North's "Low Level of Federation" Idea. But the two contradict in point of the character and composition of pre-unification transitional system, the official name and future vision of the Unified Korea and so on.