There were 3 subfacies including delta-front，prodelta and deep lake，and 10 microfacies including underwater distributary channel，tributary bay，channel mouth bar，distal bar，prodelta clay，sandy debris flow，turbidity current，fluidized sediment flow，slump deposit and deep lake mud of the Upper Triassic Yanchang Formation Chang 6₃ interval in Huanxian area by detailed core observation，combined with logging data integrated analysis.A series of sedimentary microfacies profile maps and sedimentary microfacies distribution maps of Chang 6₃ interval show that delta-front subfacies developed in western，northern and northeastern part of the study area，deep lake subfacies including deep lake mud，sandy debris flow and turbidity current developed in central and southeastern part of the study area.The authors firstly proposed that sand sediments can transport from shallow water area to deep water area through a series of water channels on prodelta to form the gravity flow deposit.On the comprehension of above studies，the sedimentary model of study area was established. This paper finally analyses the hydrocarbon potential and points out that underwater distributary channel and sandy debris flow sedimentary microfacies are the best reservoirs in the study area.These sand bodies generally pinch out to form big lithological traps. The study area is the favorable lithologic reservoir exploration target zone.