The two-phase cyclone separator can complete concentration of the slurry and liquid clarification. In order to explore the internal flow field and separation characteristics of the two-phase cyclone separator, the three-dimensional flow field inside the two-phase cyclone separator was numerically simulated by Fluent of the CFD software using the RNG k-ε turbulence model. Then, the distribution of parameters such as the pressure, velocity, volume distribution, turbulent flow energy, and turbulent dissipation rate were obtained. The results showed that the internal radial velocity of the two-phase separation cyclone gradually increased from the center to the outside, and gradually decreased approaching the separator wall, showing an “M” type hump distribution. The axial velocity was symmetrically distributed and the maximum value appeared at the overflow opening and the bottom opening. From the flow trajectory of the ore particles and water inside the cyclone, it could be seen that after the slurry turbid liquid entered the cyclone separator from the tangential inlet, the ore particles and water rotated at high speed inside the cyclone separator to form an external swirling flow and internal swirling. The heavier density of the ore particles flowed out from the lower bottom opening, and the lighter density water flowed out from the upper overflow opening. The simulated two-phase separation efficiency reached 86.93%.