Abstract: By employing the solubility of sodium hydroxide or potassium hydroxide in small molecular alcohols including methanol and ethanol，alcohol extraction is usually used as an approach for separating sodium hydroxide or potassium hydroxide from their solid mixture with other water soluble compounds.The separation processes of caustic soda by vacuum distillation of methanol from the CH3OH-NaOH-H2O ternary system were investigated.The conditions for initial processes were determined by investigating the effect of single factors，including vacuum degree，temperature，time，and alkali concentration， on methanol recovery.The optimal process conditions were determined with orthogonal experiment.Experimental analysis results showed that the recovery rate of methanol was 99.35%，the purity of the methanol was 95.1%，and the residual liquid caustic soda mass concentration was 600 g/L when the vacuum degree was 0.08 MPa，the distillation temperature was 85 ℃，and the distillation time was 60 min.The methanol and the residual caustic soda solution can be thereby separated and recovered as required.

Key words: methanol, sodium hydroxide, vacuum distillation, single factor experiment, orthogonal experiment