To investigate the separation performance of a novel liquid-liquid dynamic hydrocyclone (LLDH), a series of experiments and numerical simulations were conducted. Algebraic slip mixture model was used to simulate the multiphase flow in the LLDH, in which the turbulence was modeled using Reynolds stress model and the rotation of the walls was modeled by multiple reference frame model. The numerical results showed a good agreement with the observations and measurements in experiments. The results showed that the increase of rotation speed would strengthen the swirling intensity in LLDH and thereby separation efficiency was raised. However, increase of flow rate would decrease the residence time of oil droplets, causing reduction in efficiency. By comparison, flow split ratio had slight influence on the flow field, and the efficiency rose a little as flow split ratio increased. The efficiency of the LLDH could remain high when the nondimensional rotation rate was large enough.