The kinematic viscosity,electrochemical window and electric conductivity of BMimBF4and BMimPF6and their binary composite ionic liquids mixtures were studied.The results indicated that,physical and chemical properties of binary composite ionic liquids mixtures were changed by way of simply regulating volume of BMimBF4and BMimPF6,which brought designing ionic liquids into full play and opened a new way for the application of green solvent-ionic liquids.