The hermorrago disease of grass carp (Ctenaopharygodon idellla)is an actue infection caused by Reavirus. The symtoms of the disease is that the whole body and alI organs of the fish appears bleeding. The number of erythrocyte, Ieucocyte and. hemoglobin of the diseased fish are obviously Teas than the healthy one, ands that of artifically irzfeeted fish are much less than that of naturally dissesed fish. The bassphils is fixst found in the fish bland. The small blood vessels are extemsively damaged. and the microthrombi are formed. The muscle, intestines, livers, spleen，kidneys and gills of the fish appear bleeding， degenerated and necrotic. There are acidophilic inclusive bodies in the cytoplasm of liver cells.