From the perspective of the movie history of the centennial American Civil War, this paper expounds the collective memory and the historical reconstruction of the Civil War and post－war reconstruction of the American nation, especially the southern states, where the “Southern Myth” was born. It focuses on the analysis of the direct impact of this myth on Griffith’s The Birth of a Nation, exposes the basic pattern of the theme, and demonstrates the far－reaching influence on the following Civil－War movies within the century; henceforth it provides a cultural historical analytical framework for the future study of the American centennial Civil－War movies.