NOVELTY - An optical activity of alpha -terpinol is improved by dissolving raw material racemate or alpha -terpinol with low optical activity to solvent, adding resolving agent, heating and refluxing for 1-3 hours, controlling reaction temperature to be not lower than the boiling point of the solvent, heating, filtering, and obtaining filtrate and filter residue; decompressing and distilling the filtrate, recycling the solvent, and obtaining light yellow crystal; and dissolving crystal in eluant, blending, and heating and separating the phase.    USE - Method for improving optical activity of alpha -terpinol (claimed) useful as synergistic agent of common agricultural miscible oil or water agent insecticide, herbicide or bacteria remover.    ADVANTAGE - The method uses dehydroabietylamine as resolving agent which can be separated and purified and which is inexpensive and readily available. The separation technique is convenient to operate. The resolving agent, solvent and eluant can be recycled, thus the method is low in cost, has no pollution, and is suitable for industrial production.    DETAILED DESCRIPTION - Improving optical activity of alpha -terpinol comprises:    (A) dissolving raw material alpha -terpinol with low optical activity to solvent, adding resolving agent after complete dissolution, heating and refluxing for 1-3 hours, controlling reaction temperature to be not lower than the boiling point of the solvent, heating for 24-48 hours at room temperature, filtering, and respectively obtaining filtrate (A) and filter residue (B);    (B) decompressing and distilling filtrate (A), recycling the solvent, and obtaining light yellow crystal (C) with thick liquid;    (C) dissolving crystal (C) in eluant, blending for 0.5-1.5 hours at normal temperature, and heating and separating the phase, the upper layer being an eluant layer, and the lower layer being a separation product levorotatory alpha -terpinol;    (D) washing filter residue (B) using the same solvent, and obtaining precipitate (D); and    (E) dissolving precipitate (D) in the eluant, blending for 0.5-1.5 hours at normal temperature, and heating and separating the phase, the upper layer being an eluant layer and the lower layer being separation by-product dextrorotatory alpha -terpinol.    The resolving agent is optical pure dehydroabietylamine with specific rotation of 56.1 degrees , a mole ratio of dehydroabietylamine and alpha -terpinol being 0.7-1.1:1. The solvent is 1-4C alcohol. The eluant is carbon tetrachloride, methylbenzene, dimethylbenzene, cyclohexane and/or n-hexane.