The invention relates to the technical field of aquaculture, in particular to a method for improving water quality in aquaculture, which comprises the following steps: S1, crushing a water quality modifier, adding sweet potato starch and water, uniformly mixing, putting into an extruder, extruding, and preparing into spherical water quality improving balls by a rounding machine; and s2, uniformly throwing water quality improving balls into water once every 15 days, wherein the throwing dosage is 1-2.3 kg/1m water depth per mu of water surface; wherein the water quality improver is prepared from the following raw materials in parts by weight: 25 to 35 parts of EM bacteria, 20 to 25 parts of probiotic, 25 to 30 parts of bacillus subtilis, 15 to 25 parts of faecalis coccus, 10 to 15 parts of an algae growth accelerant, 10 to 12 parts of a compound oxygen supply agent, 10 to 20 parts of a heavy metal adsorbent and 10 to 12 parts of a photosynthesis accelerant. According to the present invention, the surface tension of the water body can be reduced, the oxygen absorption capacity of the water body can be improved, the excessive aging of algae in the water can be prevented, and the photosynthetic efficiency of aquaculture can be improved.