The invention discloses an activity enhancer for shrimps, crabs and fish in aquaculture and a preparation method thereof. The enhancer comprises the following components in parts by weight: 15-20 parts of calcium gluconate, 25-35 parts of light calcium carbonate, 15-25 parts of calcium hydrophosphate, 20-30 parts of natural anti-stress factor, 10-15 parts of amino acid and 5-10 parts of sodium percarbonate; and the natural anti-stress factor comprises the following components in parts by weight: 13-18 parts of manyprickle acathopanax root, 12-15 parts of indigo woad root, 9-12 parts of baicalskullcap root, 9-12 parts of cape jasmine fruit, 7-10 parts of artemtsm, 6-8 parts of Chinese angelica, 6-8 parts of raidx astragali, 4-7 parts of rheum officinale, 4-7 parts of campanumaea pilosula,6-9 parts of salvia miltiorrhiza bunge, 5-7 parts of tree peony bark and 5-8 parts of uncaria. The preparation method comprises the following steps: adding the raw materials into a reaction kettle for stirring and mixing; heating the reaction kettle, standing and curing to obtain a finished product; and the natural anti-stress factor is prepared by crushing the materials into powder. The invention provides an ecological preparation with high nutrition, no antibiotic and no harmful chemicals for shrimps, crabs and fish.