The two different common accessible ionic liquids [BMim][BF4] and [BMim][Tf2N] were mixed each other in a simple and economic way. In some compound ratios, the dynamic performance of nitrobenzene in electric reduction was superior to that of any single kind of ionic liquid has been appeared. The interaction and mass transfer of diffusion of nitrobenzene in composite ionic liquids with different volume ratios were studied with molecular dynamics (MD) simulation. The improvement of the electroreduction performance of nitrobenzene in composite ionic liquids was verified and was tried to explain. This provides a new idea for the modification and functionalization of ionic liquids in electrochemical field. The experimental results showed that kinematic viscosity and electroconductibility of different ionic liquid systems display a regular change. And the change law has been basically unchanged after adding water. The two different functional ionic liquids were complemented each other in a simple and economic way, which has compensated for the disadvantage of mono-component ionic liquids. At 25 degrees C, electroreduction property of V-[BMim][BF4]:V-[BMim][Tf2N] = 1:1 is the best in cyclic voltammetry experiments of nitrobenzene in different composite ionic liquids. Its electrochemical behavior is significantly affected by scan rate, temperature, concentration of nitrobenzene and concentration of water. The MD simulation results showed most of interaction energies between nitrobenzene and different ionic liquids with and without water is little difference. The variation trend of diffusion coefficients in different composite ionic liquids is consistent with that of interaction energies. Analyzing pair correlation functions showed that the bonding and nonbonding interactions are formed between the N, S and O atoms of ionic liquid and the N and O atoms of nitrobenzene. The diffusion is mainly caused by the nonbonding interaction between nitrobenzene and composite ionic liquid, and the interactions with water molecules are obviously greater than that without water. The conclusion is consistent with the experimental results. (C) 2014 Elsevier Ltd. All rights reserved.