A new model is proposed here to estimate melting points of imidazolium and benzimidazolium ionic liquids (ILs) from chemical structures by using a group contribution method, which considers the contributions of normal groups, ionic groups, and characteristic factors of molecules. The melting points of ILs are fitted by the equation presented in this study. Thirty simple groups and three characteristic factors were defined in the model based on the optimization of property values of 155 ionic liquids. The average relative deviation in this work is less than 5.86%, and calculated values of an additional 35 ILs are compared with the values in the literature. The R-2 for 190 ILs is about 0.8984. The results show that melting points of ILs determined by the method are accurate and thus the new model can be applied to predict melting points of ILs.