Abstract: The systematic studies of the sedimentary characteristics, sedimentary microfacies and sedimentary evolution of the 3rd member of Quantou formation in Xinli oilfield of Songliao basin show that during the deposition of the 3rd member, the basement of this basin was in slow settlement and gentle terrain, and the meandering river sediments were formed under the background of alternating humid and arid climate appearance. This paper identified 6 types of sedimentary microfacies, such as point bar, abandoned channel, flood land, natural levee, crevasse splay, flood plain, and presents the plane graph of sedimentary facies, which could be as a geological basis for further exploration and development in this oilfield