Rotating packed bed (RPB), in which high gravity is simulated by a centrifugal force, plays an important role in process intensification of fluid mixing and mass transfer. However, uneven initial liquid distribution in RPB leads to poor micromixing efficiency in local areas of the packing. Therefore. a premixed liquid distributor is proposed in this work to improve the liquid distribution in RPB. Micromixing efficiency of RPB with the premixed liquid distributor was studied by adopting the iodide-iodate reaction as working system and show better micromixing efficiency compared to that of RPB with non-premixed liquid distributor. Also, the effects of operating conditions (e.g. rotational speed, acid concentration, volumetric flow rate) and geometries using the premixed liquid distributor on micromixing efficiency (characterized by segregation index X-s) were investigated. The results show that segregation index X-s decreases with the increase of rotational speed, and the decrease of acid concentration and volumetric flow rate. (C) 2009 Elsevier B.V. All rights reserved.