In this work a numerical simulation is studied to investigate the motion of single bubble in ionic liquids using an improved volume-of-fluid (VOF) method. In the improved method, besides the gravity and surface tension, a new drag force is added to the momentum equation in order to describe the gas-liquid interaction in the ionic liquids, which possess some special properties compared with the traditional solvents. The deformation, velocity and equivalent diameter of single bubble rising in three ionic liquids, i.e., bmimBF(4), bmimPF(6) and omimBF(4), are simulated and the calculation results agree well with the experimental data. Furthermore, the detailed velocity fields and pressure fields around the bubbles are predicted with the proposed numerical simulation model. This work is important for understanding the fluid dynamic performance of bubbles in ionic liquids, and could provide a useful tool for designing a bubble column with ionic liquids as its solvents. (C) 2010 Elsevier Ltd. All rights reserved.