NOVELTY - Antibacterial fishing medicine comprises (in wt.%) chitosan (16.5-78.5), starch (18-80) and animal antibacterial medicine (1.2-20).    USE - Used as an antibacterial fishing medicine.    ADVANTAGE - The medicine is not dissolved in the water, it does not pollute the water and can be degraded in the water or the fish naturally, and the degradation product does not have the toxic or side effect in the environment, the medicine is released in the water slowly, thus most medicine can be eaten by the aquatic animal. The medicine has high feeding efficiency, convenient feeding, thus it is safe and environment-friendly, and it can adapt to various kinds of fishes and animals.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for preparation of the antibacterial fishing medicine, comprising: (i) adding chitosan slowly into acetic acid solution with concentration of 1-5% by several times, heating the solution in water bath at 50-70 degrees C and dissolving the chitosan to obtain chitosan acetic acid solution containing 2-8% of chitosan; (ii) adding the starch slowly in the chitosan acetic acid solution by several times, and stirring the solution to obtain chitosan/starch solution system containing 2-9% of starch; (iii) adding the animal antibacterial medicine in the chitosan/starch solution and stirring to obtain liquid antibacterial fishing medicine containing 0.2-1% of the animal antibacterial medicine; (iv) stirring the liquid antibacterial fishing medicine, increasing water bath temperature to 80-90 degrees C, then heating and curing the starch until the liquid antibacterial fishing medicine is colloidal; (v) removing the colloidal antibacterial fishing medicine out of a water bath pot, cooling it for 5-10 minutes, pouring it slowly and uniformly into a prilling die plate and cooling; (6) dipping the die plate to the sodium hydroxide solution with the concentration of 0.1-10 M, washing it repeatedly for 3-5 times at the time intervals of 5-7 minutes, then taking out the die plate and stewing it for 30 minutes until the acetic acid in the antibacterial fishing medicine is neutralized completely; (vii) introducing the die plate into pure water to wash for 1-2 times, removing the sodium hydroxide solution; (viii) introducing the die plate into a refrigerator at -40 degrees C and freezing it for more than 20 minutes after the PH of the antibacterial fishing medicine is 7; and (ix) introducing the die plate into a freezing drier to freeze and dry for 24 hours to obtain grain antibacterial fishing medicine.