Nangqen basin is a typical representative of the medium-mini-type Paleogene basins controlled by local NNW-treading faults distributed along Jinsha River-Red River belt on the northeastern margin of Qinghai-Tibet plateau. Gonjo Formation is perfectly developed and dominated by a set of thick-bedded, purplish red, red terrigenous clastic rock formation containing gypsum rock in association with large-scale high potassium rocks in Nangqen basin. Combined with results of field geological investigation and analysis and determination of samples as well as quantitative studies of the sandstone framework detrital composition of the Paleogene strata, the authors systematically analyzed petrologic characteristics of the sandstones of the Gonjo Formation in Nangqen basin in the framework of the basin evolution. According to the analysis of geochemical features of sandstones of the Gonjo Formation, the characteristics of paleoclimate, paleoenvironment and provenance in the study area were revealed. For sandstones in different strata of Gonjo Formation, systemic sampling and determination were conducted, the detrital composition of sandstone was observed under a microscope, and the sandstone framework detrital composition was calculated and analyzed using the line-count method. The quantitative data of the clastic constituents not only constitute the nomenclature foundation of sandstones but also provide an important basis for understanding the nature of the sedimentary basin and estimating the provenance region. Meanwhile, the data processing methods included the genetic classification of the clastic constituents and the triangular graphical analysis. According to the theoretical analysis and the results of Dickinson W.R, the authors analyzed and discussed the relationship between the provenance and the plate tectonics of clastic rocks of Gonjo Formation. The results indicate that the sandstones of Gonjo Formation belong to recycling orogenic belt area, and only the samples of Eg² came from polycyclic orogenic belt area and cratonic interior. From the viewpoint of geological features as well as the position of composition plots, it is considered that the provenance evolution began from stable cratonic interior to lithic recycling orogenic belt and polycyclic orogenic belt area. The trend of the composition maturity in the sedimentary successions from Eg¹ to Eg⁵ was low-high-low. Provenance evolution analysis shows that the tectonic movement was very intense in the northern and northwest parts of the basin during the early deposition, which provided the period of the 2nd member (Eg²) with low maturity detritus. From Eg¹ sequence to Eg² sequence, with the increasing strength of the tectonic movement, the content of feldspar had a decreasing tendency while that of lithoclast had an increasing tendency. And the alluvia fans, i.e., the fluvial facies were at the primary stage of development. In terms of Eg³, the tectonic movement began to taper off, the content of feldspar increased, and lithoclast decreased gradually, which however brought about the end of lake sequence development, with strong uplifting and erosion in northwest and north parts of the basin, the deposition heaped up in the depressions, and the existence of igneous activities in east and south parts of the basin. As for Eg⁴ and Eg⁵, the provenance changed into a transitional recycled orogen, and the content of feldspar presented an increase-decrease tendency, while the tendency of lithoclast content was on the contrary. Through an analysis of the changes of the detrital composition of sandstone, Nangqen basin underwent two stages of tectonic evolution in which the early stage belonged to the reverse-compression and the late stage to strike slipping-compressional deformation. The evolution trend of tectonic evolution combined with the detrital composition changes in each sequence was studied. An analysis of the major elements of sandstones indicates that felsic rocks were dominant in the provenance, accompanied by mafic rocks. Varying tendency of chemical index of weathering (CIW) is similar to that of the chemical index of alteration (CIA) from Eg¹ to Eg⁴,and this index is used to reflect the weathering intensity from weak to strong and to weak again. Variation of the index of compositional variability indicates the circle of lower compositional maturity-higher compositional maturity-lower compositional maturity from Eg¹ to Eg⁴ in the section, suggesting that geological conditions of the provenance region had significant differences. The paleo-climatic environment changed from warm-moisture through drought-hot to moisture in upward succession during the depositional period. The provenance of the sediments of Gonjo Formation was based on felsic rocks, with the provenance of Eg³ sequence having a small quantity of mafic rocks, probably due to the movement of shear-strike slip faulting that resulted in gradual extension to the upper mantle and induced partial melting of basement materials which erupted or intruded into Eg³ sequence.