Although a series of achievements has been obtained through several degrees of exploration, there remains no obvious breakthrough in oil-gas exploration in the South Qilian Basin. In such cases, combined with previous studies, according to the field geological survey for marine hydrocarbon source rocks through outdoor profile surveying, and collecting samples in systematically, and comprehensively evaluated the maturity, type and depositional enviornment of Permian hydrocarbon source rocks by analyzing kerogen and measuring saturated hydrocarbons of source rocks with gas chromatography and mass spectrometer, and by analyzing of major elements, trace elements and rare earth elements. The results indicated that source rocks in a hypoxic and high degreee reducion and high salinity depositional environment in Permian. The source rock of mud organic matter were coming from woody parts of terrestrial higher plants, and their organic matter type Ⅱ2, with a single source and high maturity, being a favorable source rock in the study area. While source rock of carbonate organic matter has the characteristics of duality, which coming from terrestrial source and underwater creatures, and their organic matter mainly type Ⅲ and part of type Ⅱ2, with moderate maturity, being also a favorable source rock in the study area. The main components of Permian sedmints mainly from feldspar-quartez rocks and from the upper crust, be in a impact of certain enrichment. Between Gangcha sag and Halahu sag, the Gangcha sag with humid environment of higher degree heat, deeper water and higher salinity of oxidizing environment, while Halahu sag with drying enviornment of lower degree heat, lower water and lower salinity of oxidizing.