Abstract：The Dounan manganese deposit is a large-size sedimentary manganese deposit in southeastern Yunnan, and a study of its genesis can reveal the model of sedimentary manganese deposits in southeastern Yunnan. Samples from the Dounan manganese deposit were systematically studied by means of manganese phase analysis and IR spectroscopy. Based on a study of the relationship between the type of manganese and redox interface, the authors hold that the model of sedimentary manganese deposits is controlled by redox interface changes caused by sea level changes.