NOVELTY - Extracting beta-carotene in salt algae by inorganic alkali, involves: adding water to salt algae mud or salt powder, cooling to -40 degrees C, freezing for 20-30 hours, and thawing; adjusting pH to 8-9 by inorganic aqueous alkali at 45-55 degrees C and extracting for 3-5 hours; centrifuging extracting solution for 8-12 minutes at 2500-3500 rpm; using inorganic acid to adjust pH of clear liquid to 4-5 and obtain beta-carotene precipitate; and centrifuging at 2500-3500 rpm for 9-11 minutes, and removing supernatant to obtain beta-carotene, which is then freeze-dried.    USE - For extracting beta-carotene in salt algae (claimed), where beta-carotene is used as precursor of vitamin A that is useful for skin and mucous membrane cell normalization and maintaining normal retinal function; and further beta-carotene is useful for improving immunity, eliminating damage caused by free radicals, and preventing cancer, cardiovascular disease and aging.    ADVANTAGE - The method for extracting beta-carotene in salt algae by inorganic alkali, overcomes shortcomings associated with existing technology such as use of organic solvent as in organic solvent extraction method to obtain residual beta-carotenes, and supercritical extraction having large investment/cost i.e. less economic. The method can simply and quickly damage salt algae cell outer membrane composed of glycoprotein and arginine film, and exposes protoplasm. The method is simple and feasible without organic solvent residue, is low cost due to use of inorganic alkali for extracting beta-carotene in salt algae, extracting period is short, is convenient, fast can saves time, extracts beta-carotene with higher purity, and does not cause pollution to environment i.e. is environment-friendly method. The method further provides convenience, by avoiding removal of organic solvent such as acetone or petroleum ether, during subsequent extraction of polysaccharides. Thus method breaks limitation of organic solvent extraction, and is suitable for large-scale industrial production.    DETAILED DESCRIPTION - Method for extracting beta-carotene in salt algae by inorganic alkali, involves: adding water to salt algae mud or salt powder, cooling to -40 degrees C, freezing for (20-30, preferably 22-26) hours, and then thawing in (25-35, preferably 30-32) degrees C water bath until no ice crystal is seen; adjusting pH to 8-9 by inorganic aqueous alkaline solution at 45-55 degrees C and extracting for 3-5 hours; centrifuging extracting solution for 8-12 minutes at 2500-3500 rpm; using inorganic acid to adjust pH of clear liquid to 4-5 and obtain beta-carotene precipitate; and centrifuging at 2500-3500 rpm for 9-11 minutes, and removing supernatant to obtain beta-carotene, which is then freeze-dried.