Abstract: Based on field outcrops, boreholes, cores, thin sections and experimental data, this paper systematically studies the type, evolution and sedimentary model of lacustrine carbonate rocks from the Upper Member of Paleogene Xiaganchaigou Formation in Yingxiongling structural belt of Qaidam Basin and characterizes the lithofacies paleogeographical distribution combined with borehole-seismic data analysis and paleogeomorphology restoration, and points out the next favorable prospecting direction. The study shows that the Upper Member of Xiaganchaigou Formation in Yingxiongling structural belt is dominated by three types of carbonate rocks, i.e., algal limestone, granular calcareous dolomite and micritic calcareous dolomite, most of which have hybrid sedimentation characteristics, and have undergone three sedimentary evolution stages from early to late, namely brackish water, saline water and salt lake. Lacustrine carbonate reservoirs present the strongly heterogeneous properties due to the difference of mineral composition and rock texture, among which algal limestone has the best reservoir performance. There are three types of vertical lithofacies assemblages in reservoirs, which are developed in different positions of the lacustrine basin. Two sedimentary models, namely sag-uplift and gentle slope, were established. It is revealed that the lake level fluctuation and input of terrigenous detritus controlled the single layer thickness of different lithofacies, and the micro-paleogeomorphology controlled the distribution of different lithofacies assemblages. The early and late lithofacies paleogeographic characteristics of the Upper Member of Xiaganchaigou Formation show that the assemblage of micritic calcareous limestone and granular calcareous dolomite is mainly distributed in the coastal area and uplift area of Yingxi-Ganchaigou-Youyuangou gentle slope, with a superposition area of about 600 km², indicating a favorable exploration direction for the next prospect for conventional oil and gas reservoirs. Laminated micritic calcareous dolomite is mainly distributed in the semi-deep lacustrine sag of Youyuangou and its east area, with a superposition area of up to 2 500 km², providing is a favorable exploration direction for the next prospect for unconventional intra-source oil and gas reservoirs.