The interaction between inlet concentration and inlet velocity is vitally important for the regulation of a hydrocyclone, but the interactive mechanism is still unclear. This study investigated the effect of inlet concentration on the hydrodyclone's separation performance within a wide range of inlet velocity via numerical analysis. Numerical results demonstrate that the number of the dislocated particles was enhanced at a too great or a too low inlet velocity, thereby leading to the decline in the separation performance. The results are appropriate for the pre diction of the particle distribution. In addition, intense interaction existed between inlet concentration and inlet velocity. At a low inlet velocity, the cutting size and the separation precision exhibited no regular changes with the increasing inlet concentration. The cutting size and the separation precision changed alternately as the inlet concentration changed within 1% similar to 9%. This is mainly due to the fact that, despite of the enhanced interaction among particles, the turbulence intensity dropped gradually with the increasing inlet concentration. The combined actions led to the above alternate change. As the inlet concentration increased to over 20.25%, the interaction among particles far exceeded the effect induced by the decline in turbulence intensity, and therefore, the cutting size increased rapidly and the separation precision dropped. Certainly, the decline in the interaction among particles reduced both tangential velocity and axial velocity, which then destroyed the stability of the flow field and uniform distribution of particles in radial direction. As the inlet velocity increased, the cutting size increased with the increase of the inlet concentration, accompanied with the weakened cutting capability. High-quality hydrocyclone can be obtained at an inlet velocity of 5-8 m/s and an inlet concentration of 1% similar to 9%. When the inlet concentration was fixed at around 20.25%, the separation performance reached the optimal at an inlet velocity of 15 m/s. conclusively, appropriately increasing the inlet velocity can lower the adverse effect induced by the fluctuation of the inlet concentration, which can contribute to achieving the expected cutting size and enhancing the separation precision. (C) 2020 Published by Elsevier B.V.