In order to achieve the high-efficient extraction of polysaccharide from Lithothamnion superpositum,the hot water method and ultrasonic assisted method were used to extract the polysaccharide,and the methodology was systematically evaluated.Meanwhile the antioxidant activity of the crude polysaccharide in vitro was analyzed.The results showed that the yield of crude polysaccharide (9.83%) of traditional hot water method was higher than that of ultrasonic method (8.47%),but it contained more protein and polyphenol,resulting in the content of polysaccharide (64.71%) lower than that of ultrasonic method (65.55%).The results of antioxidant experiments in vitroshowed that the polysaccharide extracted by ultrasound had a high scavenging efficiency on DPPH free radicals.To sum up,this study confirmed that ultrasonic method is more suitable to extract polysaccharide from coralline than hot water method,which provides methodological support and data support for the efficient extraction and quality evaluation of Polysaccharide from coralline.