The effects of dichloromethane (DCM) and toluene (C7H8) on the microstructure, physicochemical properties and aluminum electrodeposition with 1-butyl-3-methylimidazolium chloride/aluminum chloride ([BMIM]Cl/AlCl3) were studied by quantum chemistry and molecular dynamics simulation. It is found that DCM is easy to form hydrogen bonds with anions and cations of ionic liquids. It is distributed between anion and anion, which make the distance between anion and cation increase and the interaction energy decreases. As a result, the diffusion ability of anions and cations is enhanced, and the aluminum complex anions tend to exist in the form of Al2Cl7-. The viscosity of the system decreases and the conductivity increases, so the electrochemical properties of the system are significantly improved, which are in good agreement with the experimental values. C7H8 is mainly located around cations of ionic liquids and has strong interaction with cations, which mainly plays the role of leveling agent. The diffusion ability of DCM is the strongest in the system, which can reach the electrode surface first and reduce the effective area of the electrode, which is conducive to promoting the formation of an aluminum crystal nucleus. Therefore, DCM is more favorable for electrodeposition of aluminum than the aromatic hydrocarbon C7H8.