Green tide outbreak results in massive Ulva prolifera accumulation in coast China. Because Ulva prolifera has high proportion of cellulose content, it can be used as the raw material for manufacturing bio-ethanol when cellulose degradation produces oligosaccharides. In this study, by using Congo red staining method, eight larger lysis zone strains which have the ability of cellulose-decomposing were obtained from rotted Ulva prolifera and green tide outbreak sea area. Cellulose enzyme activity characteristics and the ability to decompose Ulva prolifera of each strain were studied and high cellulose enzyme activity strains were identified. Enzyme activity of FPA and CMC in strains H3, H4, H6 and Q1 was higher than others, and carboxymethylcellulose as carbon source induced enzyme work best. Enzyme activity of CMC in the strain H3 was the highest (56.98 U/mL). And the best reducing sugar yield were 10.4% and 12.8% from strain H3 and strain H4. All the four strains were obtained by morphological identification and molecular biology identification.The experiments show that Ulva prolifera can be used as a raw material for preparation of bio-ethanol, and the screened strains can used for cellulose degradation.