Liquid-liquid equilibrium (LLE) data for the quaternary systems of ethanol + butanol + octane + water and ethanol + butanol + nonane + water were obtained at 298.15 K under atmospheric pressure in this article. The nonrandom two-liquid (NRTL) equation was used to correlate the LLE data, and the two quaternary systems were used to regress the interaction parameters of the model. The obtained interaction parameters of NRTL model were used to predict the LLE of the quinary system ethanol + butanol + octane + nonane + water and was compared with the experimental values. The results showed that the calculated values coincided with the experimental data well, an indication that the NRTL model and the interaction parameters obtained from quaternary systems could be used to predict the LLE data of quinary system. The LLE data of the quinary system were also characterized by the distribution coefficient and the selectivity, and the results showed that the ethanol aqueous solution which contained about 40 wt % ethanol was suitable for separating butanol from the butanol octane nonane mixture.