Abstract: Response surface methodology was applied to optimize the extraction of alkali-soluble polysaccharides from Enteromorpha prolifera.The factors investigated included alkali concentration,water/substrate ratio and extraction time.A three-level three-factor Box-Behnken design was applied for the experiment.The results showed that the optimum conditions for the alkali-extraction were: temperature at 100℃,alkali concentration of 0.85%,water/substrate ratio of 1/60,and extraction time of 124 min.The resultant extract contained 13.42% polysaccharides.