Abstract: Main reservoirs of Xia 9 well block in north-west edge of Junggar basin are of Baikouquan Formation and Kexia Formation in Triassic and Badaowan Formation in Jurassic, and are of middle-low porosity and low permeability on the whole.The pore structure of Badaowan formation is best and the reservoir is dominated by sandstones,while the pore structure of Baikouquan and Kexia formation is comparative poor and all kinds of conglomerates and glutenite rocks are in the ascendant.From Baikouquan formation to Badaowan for- mation,the overall physical properties of the reservoirs be- come better gradually,the content of sandstone increases, the dissolution enhances,but the cementation and the com- paction weaken with the decrease of burial depth.In addi- tion,the porosity of reservoirs increases along the axial lobe of plunging anticline and the level from southwest to north- east.The above characteristics of reservoirs chiefly result from the matching relationship of different main diageneses, the lithologic divergence and the sedimentary facies.