The T-junction is a novel type of separator used in the petroleum and gas industry. It is used to achieve the gas-liquid or liquid-liquid two-phase separation. To obtain an applicative T-junction separator, in the present study, the gas-liquid two-phase separation characteristics in multiple inclined T-junctions were investigated through a series of numerical simulations and field experiments. Two representative multiphase modes, namely, the Euler model and the mixture model, were chosen for this study. Comparisons of the field experiments were made to obtain a highly accurate simulation model. The mixture model was chosen to be better suited for this study. It is used to investigate the gas-liquid two-phase flow and the separation behaviors, which include the effect of inlet flow velocity, inlet bubble diameter, and the split ratio of two outlets. The results indicate that the best flow split ratio exists when the two-phase separation reaches the best consequence, and the best flow split ratio changes when the separation demands of gas or liquid are different. Furthermore, the separation efficiency keeps decreasing as the inlet velocity is increased. Hence, the inlet mixture velocity should be reduced to improve the gas-liquid two-phase separation. More specifically, to obtain a better separation for the same throughput, the size of the T-junction should be increased. Moreover, the separation efficiency increases as the inlet bubble diameter increases. Consequently, the results can be used to design the T-junction as an industrial separator, which can then be directly used in petroleum and gas production.