A new approach named volumetric connectivity index (VCI) based on the physical observable volumes of groups and the concept of molecular connectivity index is proposed for the prediction of the density of ionic liquids (ILs). The capability of VCI in the prediction by combination of group (formula units) volumes for a new and as yet not prepared modification can provide an estimate of the density of that compound. In this work, the densities at room temperature of 142 pure ILs including imidazolium, pyridinium, pyrrolidinium, piperidinium, quaternary ammonium, and quaternary phosphonium are estimated by this new model, and the results are compared with the experimental data collected from the most commonly used literatures. The average deviation for the prediction of all the 142 ILs is only 0.63%, and R-2 and rmsd are 0.9971 and 0.01214 g . cm(-3), respectively. Combined with a model called mass connectivity index (MCI), the new model can also be used to predict the densities of ILs at different temperatures accurately with the room temperature density obtained input in MCI.