Abstract: Nanyishan structure,located in the north of the western Qaidam basin in Qinghai province,belongs to a third-level structure in the western Mangya depression area of Nanyis-han anticline belt.After coring and mud logging analysis,the target layer is found to be in a mixed sedimentary facies,mainly composed by carbonate and sandstone.Through anal ysis and research of profile sedimentary characteristics,faci es sequence,and microfacies distribution of main oil-bear ing layers,in combination with geologic data and on the ba sis of facies sequence grading rules,the sedimentary facies characteristics of Youshashan formation in Nanyishan struc ture of Qaidam basin has been summarized in this paper.