Liquid-liquid equilibrium (LLE) data of the ternary system 2-methyl-2-butanol + water + o-xylene were determined at 303.2, 313.2, and 323.2 K under 101.3 kPa. The extraction capacity of o-xylene is expressed by selectivity, which is more than 118 and decreases with the increase of temperature. The quality of the experimental LLE data is verified by calculation of the overall mass balance and alignment between the conjugated phases and overall compositions. The experimental LLE data were regressed by the NRTL and UNIQUAC models, and the binary interaction parameters were obtained. And the root-mean-square deviations (RMSDs) are less than 1.02%.