The toxic effects of the heavy metals on fish, the accumulation ofthe hoavy metals in the different part of fish body and the relationship between theheavy metals and the deformation of fish are emphatically investigated; The resultsshow: (1) the quantity of various heavy metals in the deformed fish is much higherthan that of the normal fish; (2) the elder of the age of fish,has the more of accumu-lation of heavy metals: (3) the accumulated quantity of heavy metals in liver, kidneyand spleen is higher than in other parts of the fish body; (4) the accumulation ofheavy metals in fish can not only be estimated,but also gradually increases year byyear even the fish live in mild polluted water; and (5) cadmium is a high effectiveheavy metal on deformation. The toxic effects of the heavy metals, including zinc,lead,copper and cadmium, on the embryoes and fries of the fish are emphaticalystudied. At the same time certain practical polluted situation is imitated. The toxicexperiments indicate that all of these four heavy metals have definite toxic effectto fish embryoes and fries. The more the concentration, the higher the toxic effect.The mixed solution has higher toxic effect than that of the single solution. In themixed solution, some combination, for examplem, zinc and cadmium produce antagonismin low concentration.Pathological changes of the tissues in some organs are also studied. Microsection shows that (1) organs of the younger fish are all in the normal range, but (2) theelder fish has higher accumulative quantity of heavy metals. Fatty degeneration in thehepatic tissues and lipofusion overaccumulates in the melanomacrophagocyte of thehepatic,renal and splenic tissues. These phenomenon have certain relation to patholo-gical changes,It is need to do further research work.