The invention relates to a novel method for extracting a seaweed intermediate by an 
enzyme process, which comprises the following steps: sufficiently cleaning and immersing dry 
Laminaria digitata, adding into an acidic solution, and stirring uniformly to obtain a mixture A; dissolving a composite acidic 
enzyme in water, and adding into the mixture A to perform primary stirring extraction, thereby obtaining a mixture B; dissolving an inorganic alkaline compound and a composite alkaline 
enzyme in water, and adding into the mixture B to carry out secondary stirring extraction, thereby obtaining the mixture C; and dissolving a preserving agent in water, adding into the mixture C, and stirring uniformly to obtain the seaweed intermediate. The method for preparing the seaweed intermediate is efficient, quick, mild, comprehensive, safe and harmless. Compared with the traditional acid-alkali extraction technique, the extraction efficiency is enhanced by 50% above, the 
algal polysaccharides content is enhanced by 50-100%, the 
alginic acid content is 3.5-4.0, the effect of the seaweed 
intermediate product is obviously enhanced, and all the effective components in the seaweeds are reserved in the product, thereby implementing complete-effect addition in deed.