The invention discloses a water quality improvement agent for aquaculture. The water quality improvement agent for aquaculture is mainly prepared from nano-silver, glycine betaine, saccharicterpenin, amino acid, potassium dihydrogen phosphate, photosynthetic bacteria, bacillus subtilis, vitamins, biological enzymes and traditional Chinese medicine, wherein the traditional Chinese medicine includes, by weight, astragalus, andrographis paniculata, isatis roots, houttuynia, plantago, poria, licorice, notopterygium, parasitic loranthus, schisandra, mulberry leaves, cuscuta, honeysuckle, prunella vulgaris, corydalis, folium artemisiae argyi and parsnip. According to the water quality improvement agent, the nano-silver is adopted for sterilization, a medicine stone provides a large number of microelements, the composition prepared from the traditional Chinese medicine serves as an antidisease immune adjusting agent of the water quality improvement agent, the effects of strengthening constitution of aquatic animals and improving the anti-stress capacity and immune disease resistance of the aquatic animals are achieved, and the rate of survival of the aquatic animals is increased. A preparation method of the water quality improvement agent is simple in preparation process and easy to master.