Abstract: Of all flow patterns encountered in multiphase flow field operations, slug flow is the dominant one. Classical flow maps show that the intermittent regime exists for a wide range of gas and liquid flow rates. The objective of this study is to investigate two-phase slug flow in a pipeline-riser system. Thus, Volume of Fluid (VOF) method implemented in ANSYS FLUENT 16.1 is used to capture the transient distribution of gas/liquid interface through the pipe. The simulation of model parameters are the same as recent experimental study conducted by Wangetc. The inner diameter of riser and flow line is 51.4 mm. The riser is 3.5 meters high and the flow line is 12 meters long inclined downward of 4°. In the simulations, air and water were used as flowing fluids. Results of void fraction, pressure and liquid holdup are presented. The results obtained numerically with the developed model are in very good agreement with the experimental.