This paper deals with the pathophysiolagy on the hemolytic asaite-sosis of crucian carp.The cardinal symptoms of the disease is seriously producing ascites in the fish. The ascites is light yellow or red, hyaloid, slight cloudy or cloudy and solidfied for most of diseased fish. In addition, the pH of the ascites is 6.5, and the Rivalta's qualitative Test of protien is positive. Therefor, we may reasonably conclude that the ascites is egudate caused by inflammation; it is hepatic ascites but not transudate caused by oircuiatary obstruction.The contents of sodium, chlorine, glucose, total protien, albumin in serum of diseased fish is obviously lower than that of healthy fish (p<0.001)，particularly, the albumin content is lower than 1% of that of healthy fish. The creatinine and enzymes of LDH, GOT, GPT and AMY are much higher than that in healthy fish(p<0.001).The above indicates that the pathological changes in liver, kidney, heart and pancreas of diseased fish have occurred seriously; the functions of liver,kidney and pancreas have broken down and have been developing into uraemia and hepatic coma until the fish died.