The cyclone separator is a liquid-liquid separation device that has been developed very rapidly in recent years. The main advantages of cyclone separators are high efficiency, energy saving, economic space occupation, and low cost. It is widely used in such industries as mineral processing and metallurgy, sewage treatment, food, paper making, and petroleum chemistry. Therefore, it is particularly important to study the relevant characteristics of the cyclone separator. Besides, numerical simulation is an important method for the development and research of liquid-liquid cyclone separators. This work systematically introduced the research progress of the numerical simulation of liquid-liquid cyclone separators, where the effects of the selection of cyclone separator model, the variation of geometric structure (including the inlet, the cone section, the overflow pipe, the guide vane and the cylindrical section) and operating parameters (including the split ratio, the total flow and the feed ratio) on the separation efficiency as well as the flow field were analyzed, and the final evaluation indices (including the separation efficiency and the pressure drop) were also proposed. Besides, some opinions on the change of geometrical structure and operating parameters influencing the separation efficiency and the pressure drop were provided, and the numerical simulation of the vortex and the droplet breaking and coalescing, as well as the development of new separation efficiency evaluation formulas were prospected. New ideas for the following up research workers of the cyclone separator were provided.