With deepening research on the development of shale oil and gas development and related fields,transportation and deposition of fine-grained sediments have been a significant area of research in the stratigraphic community. However,muddy gravity￣flow deposits in the Mesozoic lacustrine environment in China have received little attentions. Based on core examinations,thin section identifications and comprehensive analysis,current study investigate sedimentary features of muddy gravity￣flow deposits in the Late Triassic southern Ordos Basin,and discuss their genesis and classifications. Various types of lacustrine mudstones or shales were recognized in the Yanchang Formation in the southern Ordos Basin,including muddy slumps,muddy debris flows,muddy turbidity currents and muddy hyperpycnal flows. Gravity￣flow deposits are classified into three types, namely sandy gravity￣flow deposits,muddy gravity￣flow deposits and hybrid gravity￣flow deposits. Based on mud contents and gravity flows’ originations, four types of slumps,debris flows,turbidity currents and hyperpycnal flows were inferred. And then they are classified into 12 types based on origination and mud content. Slumps and debrites mainly occur near to toe slope of delta fronts, while turbidites and hyperpycnites are well developed in large extent from delta slopes to basin plains. It is considered that (1) mud can be transported and deposited by active hydrodynamics; (2) fine-grained deposits created by gravity flows take a high percentage in lacustrine mudstones and shales; (3) muddy gravity flows are significant in transportations and depositions of clastic particles,clay minerals and organic matters, and are thus of great significance to hydrocarbon generating,reservoir capability and research on fracturing to unconventional oil and gas.