The article spotlights both the toponomic change and geographical demarcation of Southeast Asia through the governmental and the academic publications as well. It focuses on the formation of Southeast Asia, the dynamics of its composition, as well as the associated meanings behind the alternations. The discussed place names include Nan-yang, Tropical Far East, Tropical Asia, Further India, Indo-china, East India, Southeastern Asia, Southwestern Pacific and so on, whereas the disputed areas consist of the Philippines, Burma, Taiwan, Ceylon, Indian subcontinent etc. The article regards the nature of both naming and demarcating of Southeast Asia as the cultural politics on space, in which it reveals the attitudes, positions and needs of various groups of peoples, cultures, and even academic disciplines as well.