Abstract: The buried depth of Jurassic Xishanyao formation in Yongjin area,Junggar basin is up to 6 000 m and it is mainly of low permeability- ultra low permeability reservoirs.Therefore,the reservoir characteristics analysis and clear distribution of favorable reservoirs are the main research contents in the area.Through the analysis of petrological characteristics and pore structure characteristics,the reservoir space types of the reservoirs are firstly given priority to residual intergranular pore and secondarily to solution pores.Based on the influential factors analysis of sedimentary facies,formation pressure,reservoir buried depth and diagenesis,the main controlling factors of the favorable reservoirs distribution in the study area are determined to be sedimentary microfacies,abnormal pressure and unconformity reform.By taking the above factors into consideration,Yong-2,Yong-1 and Yong-3 are determined to be the favorable area for the reservoir development.