Owing to the exhaustion of onshore resources, the development of resources has been expanded to the deep subsea. As the necessity of offshore plants is steadily increasing, there is an increasing interest in studying multiphase transportation technology. Multiphase pumps differ from single phase pumps in many ways, including performance evaluation, internal flow characteristics, and complex design methods. The primary issue of multiphase flow transport technology is that the characteristics of the internal flow change according to the gas volume fraction (GVF). Many theoretical and experimental analyses have been conducted to understand the mechanism of the internal flow field in multiphase pumps. As advanced computational fluid dynamics (CFD) based on the threedimensional Reynolds-averaged Navier-Stokes (RANS) equations have become reliable tools, numerical analyses accompanied by experimental research have been applied to investigate the hydraulic performance and internal flow field of multiphase pumps. A number of studies have been conducted to investigate these phenomena. However, the understanding of the detailed mechanisms of phase separation and the forces that occur in the internal flow is not completely clear. This study aimed to establish a multiphase flow analysis method with high reliability when the internal flow of the multiphase pump is bubbly flow. To ensure the reliability of the numerical analysis, the numerical results were compared with the experimental data. Additionally, to analyze the detailed dynamic flow phenomena in the multiphase pump, the effects of various interphase forces acting between the liquid and gas phase and the particle diameter of the gas phase on the hydraulic performance were investigated.