Abstract: This paper reviews the latest advances on the variable mass flow with wall inflow in horizontal wellbores. The discussions mainly focus on the following topics: thecalculation of the horizontal wellbore flow pressure and the oil output; the formula for wall frictional factor correlation with various influx; and the mechanical analysis of flow resistance loss within the wellbore with radial inflow. Especially, the calculation of flow resistance factor of variable mass flow in introduced. The mechanism of the flowloss of two-phase variable mass flow and the advances on the numerical simulation of horizontal wellbores are also discussed.