The solubilities of o-xylene, m-xylene, and p-xylene in mixed solvents of t-butyl alcohol (TBA) and water at T = (283.15, 288.15, 293.15, and 298.15) K have been determined by spectrophotometry. The mole fractions of TBA in the mixed solvents are x = (0.000, 0.010, 0.020, 0.030, 0.040, 0.045, 0.050, 0.060, 0.080 and 0.100), respectively. The Gibbs energies of hydrophobic interaction (HI) for the aggregating process of two methane molecules with one benzene molecule in the mixed solvents have been studied, and the effects of solvent structure and solutes gathering state on the strength of HI have also been discussed.