Abstract: Response surface methodology was utilized to optimize ultrasonic wave extraction technique of phycoerythrin from Rhodophyta salina. Based on single factor test,ammonium sulfate fractionation precipitation was used to purify phycoerythrin with the tempreture,extraction power and extraction time as influential factors. A three- variable,Box- Behnken experiment design combined with response surface analysis was used to optimize the extraction technique. And the yield of phycoerythrin was selected as the response value.Results indicated that the optimal extraction process conditions were determined as 16 min,33 ℃ and 750 W for yield of phycoerythrin.Under this conditions,the yield of phycoerythrin was 15.93% with a 2.50% error compared with the actual value. Phycoerythrin had the ability to clear off superoxide free adicals( IC_(50)= 0.025 mg / m L) and ABTS free radical( IC50= 0.023 mg / m L)