Numerical simulation and experimental tests were undertaken to study the vortex stability of gas-liquid two-phase flow around a bluff body in a horizontal pipe. A 3-D Computational Fluid Dynamics (CFD) modeling is carried out in order to model the gas-liquid two-phase flow around a bluff body using a volume of fluid (VOF) model. The captured photographs of typical flow patterns are used to compare the CFD predictions and a good qualitative agreement is observed between them. The relationship between the Strouhal number and cross-sectional void fraction is derived from the experimental data. The vortex stability is analyzed in terms of frequency, Strouhal number and the requirement of vortex stability.