The bacterial gill-rot disease is a common disease of grass carp, it makes serious harmfulness to the fish. There are two types of histapathological charges: chronic and acuteness. The gill tissue of the chronic generally undergoes three worsening steps, i.e. inflammatory edexua, hyperplasia and necrosis; but the acute vng only passes through two steps: edema and necrosis, because diseased is so short that the edema passes directly to necrosis and there is no hyperplasia step. The liver and kidney of the diseased fish also show hist.opathvlogical changes,the granular denaturation and vacualation were vecured, glycogen was disappeared,up until the necrosis in liver cells. The epithelial cells in the proximal convoluted.tubules of the kidney also make same change. A number of nuclei around necrotic tubules of kidney appeared rondensated.A few of glomeruli of kidney atrophied. The quantity of leukocytes of artificially infected fish is zuurh less than the controlled one, but the erythrocytes and hymoglobin of experimental group were slightly less than the control.