The Permian source rocks were important and potential hydrocarbon forming system in the Turpan Depression, Turpan-Hami Basin, northwest China. Based on analyses of the dark mudstones’ outcrops along the surface sections, combining with geochemical data from the core samples, the paper studied the palaeosalinity of the water body in which the source rocks were deposited as well as the depositional features. The Eh and pH values of the water body were deduced from the mineral assemblages, organic carbon contents and other sedimentary factors. The sedimentary characteristics of organic matters of the source rocks were analyzed by the distribution of the source rocks and organic carbon contents as well as hosting state of the organic macerals in the main. It was discussed that the hosting state of organic matter in the source rocks could be classified into three types, namely, bedding-enrichment type, part-enrichment type and dispersion type. The source rocks of argillaceous carbonates and mudstones deposited mainly in an environment of semi-depth and deep lacustrine facies, with a high content of organic carbon, and the grey or dark grey mudstones deposited mostly in an environment of relatively shallow lacustrine facies, with less rich in organic carbon content. The green-grey or light-colored mudstones deposited mostly in an environment of fluvial or delta-plane facies, so poor in organic carbon content. It was concluded that the sedimentary zones of strong reducing environment were better positions for deposits of primary organic matter, where the organic matters could be well buried and preserved, and the source rocks were generally higher in organic contents and better in organic types.