The invention discloses a fulvic acid and lactic acid bacteria fermentation product for aquaculture and a preparation method thereof. The fermentation product is prepared from the following raw materials in parts by weight: 10-30 parts of fulvic acid, 6-8 parts of lactic acid bacteria flora, 5-10 parts of selenium-enriched yeast, 8-12 parts of bacillus subtilis, 20-30 parts of a carbon source, 0.1-0.4 part of vitamins and 50-60 parts of pure freshwater. According to the proportion, intestinal flora of aquatic animals such as fishes and shrimps are effectively improved, and corrupt molecules ofanimals and plants deposited in the bottom of a pond can be thoroughly decomposed, stink is eliminated, moss mud cakes are eradicated, the growth and reproduction of pathogenic microorganisms are strongly inhibited, the resistance ability of algae is improved, ammonia nitrogen, hydrogen sulfide, nitrite and other harmful ingredients are powerfully degraded, aquaculture water bodies are purified,harmful ingredients remaining in a culture pond are transformed into algae nutrient sources, the healthy growth of an algae phase is promoted, water color is stabilized for a long time, dissolved oxygen is improved and stabilized, the appetite of culture objects is enhanced and stress reaction is reduced; the preparation method has the advantages of simple technological process operation, low cost, and no special need for fermentation sites and equipment.