Liquid-liquid equilibria for methanol + water + hexane ternary mixtures were measured at (298.15, 308.15, and 318.15) K under atmospheric pressure. The reliability of the experimental tie-line data was determined through the Othmer-Tobias plots. Such data were essential for the product separation and solvent recycling in the process of methanol synthesis under supercritical conditions using hexane as the solvent.