Abstract: Taking the Chang-6 oil reservoir of Triassic Yanchang Formation in Maling-Qiaochuan area, Ordos Basin, as the research object, supported by petroleum geology and sedimentary stratigraphy, the paper systematically analyzes the gravity flow types, sedimentary marks, sand body distribution characteristics and sedimentary model of oil reservoirs.Based on the drilling data and observation of a large number of cores and thin sections, it is found that the sandy debris flow is in massive structure with floating muddy debris inside. The turbidity current is identified by normal-graded bedding, and density current by ripple bedding. The turbidite center and marginal microfacies, and channel-slump fan sedimentary model are established through further subdivision. The thick massive sand body caused by sandy debris flow is the favorable reservoir facies belt, which can serve as the key horizon for oil and gas exploration in deep water area.