An aqueous two-phase system containing ionic liquid, salt, and water has been widely used in extraction, but the salt used sometimes precipitates the salt out. A salt-free aqueous two-phase system is needed in this case. For this purpose, this paper studied the phase behavior of n-butylpyridine dicyanamide + isobutanol or n-butanol + water aqueous two-phase systems and determined the tie lines at 303.15, 308.15, 313.15, and 323.15 K and 97 kPa. The solubility data were obtained using the cloud point titration method, and three empirical equations that are nonlinear were used to fit it. The reliability of liquid-liquid equilibrium data was verified by fitting to the Bancroft equation and the Othmer-Tobias equation. Moreover, the phase forming ability was studied by the Setschenow-type equation. The NRTL model was used to correlate the tie-line data, and root-mean-square deviation was calculated to evaluate the fitting results. All of the equations and the model fit the experimental data very well. The graphical method was used to estimate the critical point to clear the phase behavior. Furthermore, this study also found that the lower temperature is beneficial to separate into two phases.