The purification technology of the total isoflavones from red clover was studied with a method of acid-base and water-precipitation.In the paper,the effect of alkaline solution,acid settling and the amount of water were investigated.By the orthogonal test L9(33),the optimal purification conditions are as follows:pH 8.5 of alkaline solution,pH 2.5 of Acid settling，six times of the amount of water.Under the best conditions the content of the total isoflavones from red clover can reach 50％．