Keywords: 
• percent of conglomerate fragments

Abstract: Yanqi Basin of Xinjiang is a Mesocenozoic basin, through the lithological analysis on the residual Mesozoic formation of the basin, such conclusion is reached that the source area located in the north of the basin, the debris were transported from the north to the south, so the coarse fragment were deposited in the north while fine clastic in the south; The sedimentary facies in northern basin were braided stream facies while shoreshallow lacustrine stream facies in southern basin; Concurrently, the Jurassic formation is still remained in front of Tianshan mountain of northern basin and on Kulukatag mountain of southern basin; All above show that the primary face of the basin is wider than the present one. On the basis of apatite fission track age, these Mountains began to lift in the middle of lower Crataceous. The four basins, Youedosi basin, Kuqa basin, Yanqi basin and Kumier basin, were coherent and formed the north of the larger Tarim basin before the time. The larger basin was disorganized in Late Crataceous, Yanqi basin and these basins were divided into four separate basins.