The effect of multi-inlet flow on particle classification performance of hydro-cyclones was examined experimentally and via a simulation study. The type A cyclone with two flow inlets had smaller cut size and sharper separation performance compared to the standard cyclone. Numerical simulation indicated a nearly uniform rotational fluid velocity profile for the type A cyclone. On the other hand, the standard cyclone showed a non-uniform rotational velocity profile near the inlet part of the main flow. The type B cyclone with a small additional flow injection area, showed smaller cut sizes as the flow rate of the additional flow increased. The type B cyclone showed smaller cut size compared to the standard cyclone without the additional flow. The experimental data of the type B cyclone agreed with the proposed new model based on horizontal particle separation theory. The use of a multi-inlet cyclone is quite effective at improving particle separation performance compared to the standard one.