Abstract: Crude polysaccharide was extracted from Ulva prolifera cultivated in Jiangsu using alcohol sedimentation, and some technological parameters were studied. The process of crude polysaccharide extraction was as follows:U. prolifera was submerged in 95% alcohol before filtration, the dried frond was swelled in distilled water at ratio (g/mL) of 1∶40, followed by homogenising, the suspension liquid was heated to 95℃ follow by constant temperature stirring for 15min, then separated with bolting-silk, the filter liquor was concentrate to 95% water content using constant temperature stirring, followed by centrifugalization. The supernatant was gathered and precipitated in 80% ethanol for 24h, then separated with bolting-silk. The filter residue was gathered for freeze drying of crude polysaccharide with yield of 20.1%, in which the polysaccharide content was 51%.