This paper presents a numerical study of the gas-powder-liquid flow in a standard hydrocyclone. In the approach, the turbulent fluid flow is described by the Reynolds stress model, the interface between the liquid and air core is modeled using the volume of fluid multiphase model, and the results of fluid flow are used in the simulation of particle flow described by the stochastic Lagrangian model. The flow features are examined in terms of flow field, pressure drop, volume split ratio reported to the underflow, particle trajectories, and separation efficiency. The validity of the proposed approach is verified by the good agreement between the measured and the predicted results. Discussion is then extended to other flow behavior in a hydrocyclone, including the origin of a short-circuiting flow, the structure of air core, and the motion of particles of different sizes. The model offers a convenient method to investigate the effects of variables related to geometrical and operational conditions on the performance of hydrocyclone.