Using extraction ratio as the index, the extraction process of protein from Enteromorpha clathrata was investigated using single factor test and uniform design. Results showed that the optimal water extracting conditions were as follows: pH 11.0, temperature 60℃, and extraction time 5h. The cellulase-assisted extraction condition were as follows: solid/liquid ratio 1∶50, temperature 30℃, pH 5.5, hydrolysis duration 5.5h, and enzyme dose 5.0%. The sample was first treated with cellulose, then extracted by water under the above conditions, and the extraction rate was 30.22%~35.74%. In order to utilize the protein of E. clathrata, the properties of the extracted protein were also tested. The isoelectric point (pI) of the protein was 3; foaming capability peaked at pH 7 and was enhanced with the increase of the protein concentration; the highest foam stability at pH 3 and concentration of 2mg/ml; the highest emulsifying capability and emulsion stability at concentrations of 4 mg/ml and 2mg/ml, respectively. The oil adsorption ability of the protein was found to be 131.6%, and the maximum solubility was achieved at 60℃.