Significant progress has been made in the research of sediment gravity flow and its hydrocarbon significance has been paid enough attention by oil and gas industry since 1950s. However, there still exist certain difficulties still exist when we understand the fluid types and their depositonal characteristics. Therefore, various classification schemes and different nomenclatures occurred, and in turn, this phenomenon are increases the difficulties of our understanding and awareness. Based on the recent progresses at home and a broad, the paper tries to set the record straight concerning the classification of sediment gravity flow, the corresponding meaning of the terms and their sedimentary characteristics. The reasons for chaos are manifold. Taken Miocene submarine fan in Zhujiang Formation Pearl River Mouth basin for example, the common turbidity current and debris flow and their depositon characteristics were illustrated. The common fluid transformation in gravity flow is described. At last, some problems in the research of sediment gravity flow were pointed out. The future developing direction includes breaking out the stereotype of thinking, careful use of the terms and enhancing experiment. On the whole, the study of sediment gravity flow has a long way to go.