Hydrocyclones used for solid-liquid separation are usually composed of a single cone. In this paper, we designed hydrocyclones with two cone combinations for solid-liquid separation and studied the flow field and separation performance. Simulation and experimental results showed that when the second cone remained unchanged, the angle change of the first cone had significant effect on the value of three-dimensional velocities, flow split, separation efficiency, energy consumption, and separation sharpness, but little effect on the distribution of pressure and that of three dimensional velocities, the capacity and cut size. The bigger of the first cone's angle, the smaller of the flow split and the higher the separation efficiency, the stronger of the centrifugal force, and the more the small particles in underflow. The smaller the angle change between the two cones, the larger the sharpness of the grade efficiency curve, i.e., the hydrocyclone is more suitable for the classification process. (C) 2010 Elsevier B.V. All rights reserved.