The densities and viscosities of binary mixtures of l-ethyl-3-methylimidazolium heptachlorodialuminate and tetrachloroaluminate ionic liquids with different molar compositions were measured by high-precision vibrating tube densimeter and automated microviscometer from 293.15 to 353.15 K. On this basis, the excess molar volumes and excess viscosities of binary mixtures were also calculated for the first time. All the experimental data were well fitted by the empirical equations. According to the results of computational calculations, enhanced molecular symmetry and molar concentration of heptachlorodialuminate anion usually lead to higher density. The hydrogen bonding among ions is confirmed as one of the most important structural parameters in determining the viscosity of ionic liquids. It shows that Lewis acidic 1-ethyl-3-methylimidazolium chloroaluminate can be treated as the classic binary mixtures of heptachlorodialuminate and tetrachloroaluminate ionic liquids. Looser packing and/or weaker interionic interaction probably occurs after the formation of binary mixtures. The results and conclusions of this work will help to promote future research and application of chloroaluminate ionic liquids.