Middle Triassic Zhongyou Formation in A T1 area of southern Tahe Oilfield is an important oil and gas． beating layer，of which the sedimentary type，sand body distribution，reservoir control and other kinds of geological issues are paid much attention to．Based on seismic inversion，core description and logging analysis，combined with cast thin section and grain size analysis，the sedimentary facies and characteristics are studied．The result shows that Middle Triassic Zhongyou Form ation in AT1 area of Tahe Oilfield belongs to sublacustrine fan deposits，and AA and AB type non—typical Bouma sequence are widely developed．Meanwhile，Zhongyou Formation of AT1 area mainly developed middle fan subfacies，among which braided channel，interchannel overflow，non-channel sand sheet are identified．The main reservoir sand is middle fan—braided channel．Based on the regional geologic setting，the genetic mechanism of turbidite fan is discussed and corresponding sedimentary model is established．