Abstract: With the low-temperature baked lemon pulp as material, the limonin was extracted from the lemon pulp by the aqueous two-phase system of ethanol- ( NH4) 2SO4.The effects of ethanol concentration, solid- liquid ratio, amount of the ammonium sulfate, extraction temperature and extraction time, were studied by the single factor experiments and the orthogonal tests.The results showed that when the volume concentration of alcohol was 30%, the solid-liquid ratio was 1∶25g /mL, the amount of the ammonium sulfate was 9g, the extraction temperature was 60℃ and the extraction time was 1h, the extraction rate was the most satisfactory.Under the optimum conditions, three parallel experiments were carried out and the average extraction rate reached 0.279%.The reproducibility of the experiments was well.