With the uplifting and large-scale thrusting and striking of Qinghai-Tibet Plateau, a lot of Tertiary intracontinental red basins were formed on the basis of Palaeo-Tethys multi-island ocean framework around Yushu area in the northeast of the Plateau. In these basins a set of such fluvial-lacustrine sediments as red clasolite, marlite and gypsum were deposited, accompanied by magmatism in some basins, with Nangqen basin being most typical in this aspect. Based on field petrologic and stratigraphic study, the authors divided the Gonjo Formation of Nangqen Paleogene basin in northeastern Qinghai-Tibet Plateau into five sections of different sedimentary environments such as alluvial fans, fluvialite, lake and delta facies, which formed two sequences characterized by coarse grains in the lower part and fine grains in the upper part. Different sections have different rock assemblages, suggesting that they were formed in different sedimentary environments. The first section has a limited distribution and is only exposed on the west side of the middle part of the basin; it consists of siltstone, mudstone, argillaceous limestone, shale and slate, implying lake facie deposition. The second section exposed on the north part of the basin shows a proximal and rapid deposition environment composed of red conglomerate, glutenite and sandstone. The third section has a large distribution area and is exposed all over the basin; it is composed of dark purple mudstone, silty mudstone and gypsum deposited in alluvial and fluviatile fans under the condition of dry and hot weather. The fourth and fifth sections only exposed in the middle and south parts of the basin are composed of fluvial-lacustrine sediments composed of red conglomerate, glutenite and sandstone deposited in a proximal and rapid deposition environment. An analysis of sediment sources has revealed that the material sources evolved from stable interior of craton through debris recyclic orogenic zone to mixed recyclic orogenic zone. Owing to the asymmetry of the basin and dissimilar depositional environments, different lithologic sections are exposed in different places of the basin. These data suggest that the basin has experienced the evolution history of early stage extrusion thrust foreland basin, middle stage strike-slip pull-apart basin, and late stage extrusion strike-slip foreland basin.