NOVELTY - Extracting fucosterol from Fucus involves crushing fucoidin; adding to carbon dioxide (CO2) supercritical extraction column, 1-3% ethanol as entrainer, where pressure is 20-30 MPa, temperature is 40-55 degrees C and CO2 flow rate is 3 ml/g crude drug-minute; using water saturated normal butanol for 6 stages of counter-current extraction; collecting normal butanol layer; decompressing/recycling solvent; adding to AB8 macro-porous adsorption resin column; eluting by 50%; collecting eluent; recycling ethanol and concentrating; adding methanol crystal; crystallizing; washing and drying.    USE - For extracting fucosterol from Fucus (claimed); and for extracting plant extract of algae such as rock algae.    ADVANTAGE - The method provides rock algae sterol having high purity and is easy to realize industrial amplification. The sterol is stronger and vasoactive. The method allows industrial production of fucosterol. The method provides sterol good for production operation, has low energy consumption, and creates little pollution to the environment.    DETAILED DESCRIPTION - Extracting fucosterol from Fucus involves taking fucoidin; crushing; adding to CO2 supercritical extraction column, total extraction solvent ethanol as entrainer, where the entrainer is 1-3%, the extracting pressure is 20-30 MPa, the temperature is 40-55 degrees C, CO2 flow rate to 3 ml/g crude drug-minute and the extracting time is 140 minutes to obtain extract; using water saturated normal butanol for 6 stages of counter-current extraction; collecting the normal butanol layer; decompressing and recycling the solvent; adding to AB8 macro-porous adsorption resin column; eluting by 50%; collecting the eluent 3-8 times of volume of the column; decompressing and recycling ethanol and concentrating; adding methanol crystal; separating and crystallizing; washing; and drying to obtain the product. The type of the macro-porous adsorption resin is 5 times of the volume of the column with a collection amount of the ethanol.