This article mainly focuses on the affiliation of the northern islands that have been continuing continued since World War II. After World War II, Japan, as a defeated country, was forced to accept the protocols set up by winners. Yet there are a lot of unsettled issues in the arrangements after war, therefore even so far, there are many disputes about sovereignty, This article introduces the sovereignty disputes of the northern islands, points out the obscurities in the Japanese-Russian relations since World War II, and analyzes the sovereignty of northern islands through geopolitics and international law, so that offers a relatively clear portrait of the fundamental causes, current situation, and future development of the northen islands.