The geographical characteristics and relations of Korean Peninsula appear frequently in the geopolitical classics. The countries of Korean Peninsula are surrounded by sea and land powers. As a typical Eurasian marginal zone, the geopolitical characteristics of Korean Peninsula are complex and diverse. It is not only the buffer zone of the land and sea forces as well as the bridgehead which is valued by those countries, but also an important part of maritime powers’ "island chain" to contain mainland countries, and more of a geographical "shattered area" under specific circumstances. Convenient land or sea exports to external region make Korean Peninsula (especially the unified Korean Peninsula) a significant portal area in the global geopolitical structure, and the value of it depends not only upon its location, but also upon its own national power and the features of the relationships between the countries of Korean Peninsula and the neighboring powers. Generally speaking, such a region, especially a political unit which is independent from mainland countries, is faced with the security problem of resisting the oppression of land forces on the one hand, and on the other hand, guarding against the invasion of maritime forces as well as those in the same marginal areas. Therefore, its traits of land and water are the basis of the security problems and also the cause of its turbulence. The geographical characteristics and geographical relations of the Korean Peninsula are the objective reasons of the "geopolitical destiny" that the peninsula countries are hard to get rid of. Of course, it should be noted that even if there is a so-called "geopolitical destiny", however, it is not meant to be a tragic history or an outcome, and this "destiny" can be adapted and changed through the political and strategic choices.