The invention relates to a compound premix for aquatic products. The compound premix is prepared from the following raw materials based on the percentage by 
mass of air dried substances: 10%-15% of a seaweed 
organism active extract, 5%-10% of a composite 
acidifier, 5%-10% of compound probiotics 
powder and the balance of a carrier. The invention also provides a preparation method. The method comprises the following steps: (1) carrying out 
superfine grinding on raw materials of the seaweed 
organism active extract, carrying out ultrasonic-
microwave synergistic extraction, filtering, wherein filtrate is taken as an extract liquid, carrying out enzymolysis and 
fermentation on filter residues, so as to obtain a 
fermentation liquid, respectively carrying out 
freeze drying on the extract liquid and the 
fermentation liquid, and then mixing at the ratio; and (2) carrying out 
superfine grinding on the carrier, and then evenly mixing the ground carrier with the composite 
acidifier, the compound probiotics 
powder and the seaweed 
organism active extract. According to the premix disclosed by the invention, marine 
algae resources can be effectively utilized; 
protease can be secreted; digestive absorption of 
protein is facilitated; the anti-stress ability and the 
disease resistance of organisms are enhanced; and the 
growth speed of aquatic 
livestock is improved, so that the culture cost is reduced and the culture benefits are significantly improved.