Abstract: This paper discusses the operating features of deep-well gas-lift, and describes the important role in the design and operation of gas-lift well. Based on research methods, the paper gives a literature survey of present study situation of gas liquid two-phase flow in vertical tubes in the world, and analyses the issues existing in them and limitations in their applications. On the bas is of this, the authors point out that we should strengthen the research of gas liquid two-phase flow in vertical tubes, and put forward the void fraction、two- phase density and pressure gradient correlation of ourselves. In order to obtain a reasonable and scientific classification, the authors also point out that we should study flow regime of gas liquid two-phase flow by using fuzzy set methods according to the flow features and variety of flow regime of gas liquid two-phase flow.