Abstract: The technology for extracting polysaccharides from Porphyra yezoensis was investigated. The influences of extraction temperature, extraction time and the ratio of Porphyra yezoensis weight to water volume on the yield and purity of Porphyra yezoensis polysaccharides were studied according to a current, rotational and combinational design of quadratic regression. Then quadric regression models for the yield and purity of polysaccharides were established, the extraction conditions were optimized by using above models and the optimized results were verified by experiments. The effects of removing the proteins from the extracts with hydrochloric acid and trichloro acetic acid were contrastively studied. Research results indicate that the optimized extraction for obtaining maximum yield of polysaccharides is to extract at 100℃ and 1160∶100(mg/mL) for 4.7 h; and the condition for maximum purity is to extract at 73.2℃ and 1160∶100(mg/mL) for 1.3 h. Under the optimized conditions, the experimental value of yield was (22.22±0.92)%(n=3), which was close to the estimated value(23.34％) attained by using regression model; the experimental value of purity is up to(94.60±0.90)%(n=3), which is a little less than the estimated value(98.60％). The models for the yield and purity of polysaccharides have better prediction effects. There is no remarkable difference for removing proteins as consideration of de-protein rate at pH 2.5 of hydrochloric acid(69.55%) and trichloro acetic acid(73.73%). Thus, hydrochloric acid can be used for removing proteins from extracts instead of trichloro acetic acid in industrialized production.