Abstract: The systematic studies of the sedimentary characteristic and sedimentary facies of the Permian Lucaogou formation in Jimsar sag of Junggar basin are based on the available cores, thin sections and logging data. The results show that this formation was affected by the charging of terrigenous detrital, volcanic activity and endogenous carbonate rocks, and dominated by dolomitic rock with complex rock components and varied structures. The lacustrine basin gradually changed from early open lake basin to late closed lake basin. The dessert spots are mainly distributed in such sedimentary environments as delta, underwater bank, mixed flat and dolomitic flat, etc, and characterized by thin silty layer, high contents of quartz, feldspar, carbonate mineral, and low content of clay minerals. The lower sweet spot interval has high contents of quartz and feldspar, while the upper one has high content of dolomite, between which the deposits of semi-lacustrine lake mud and gravity flow occur. Because of the periodical change of climate, the deposits appear in ring strips along lake rim to the lake center with strong heterogeneity in the vertical. In the Lucaogou formation sedimentary period, a lot of volcanic materials were carried by wind into the lacustrine basin, resulting in a mix of normal sediment, volcanic and terrigenous detrital materials in the basin