Abstract: Faulkner's full-length novel Light in August is set in Jefferson, an isolated and conservative town back against the American South. As a landmark in the Yoknapatawpha County created by the novelist, this geological space continues the spiritual trauma of the Civil War, providing a breeding ground for racial prejudice and persecution. Spatial criticism focuses on the socio-cultural attributes of space. Literary space, in turn, is regarded as a referential system with multi-dimensional denotations. The paper will adopt Lefebvre's Spatial Triad to explore the physical, the mental and the social signification of space in the target text. The inquiry of the three will map the geographic space collision between the white and the black inhabitants, the “suspect mulatto's” collapsing mental space and the suppression of the non-identity race within the white-dominant social space.