Abstract: Taking the new combined horizontal separator designed by Sub-institute, PetroChina Southwest Design Branch, as a study object, the drift-flux model of gas-liquid flow based on Euler Method is used to simulate the two-phase separation inside the separator, under the best combination condition of the components of the separator, based on CFD method, numerical simulation of the gas-liquid flow inside the separator is performed to analyze the gas-liquid separation process and separation efficiency. The simulated results are compared with test results. The results show that the new combined separator has high work efficiency, can remove liquid from natural gas effectively. Meanwhile, recommendations on the control of water tank, drainage pipe and liquid level are made in the paper.