Abstract: Both normal and artificially infected black carp aged 6—7 months were studied during 1982—1983. The structure of normal kidney tissue under optical microscope is similar to that of other freshwater fishes such as the grass carp. When the fish is infected by virus, the epithelial cells of segmental cavity in the kidney change in shape with atrophic nuclei. Under electron microscope, large vacuoles in intracytoplasmic mitochondria were observed. At the same time, many virus particles were found in inclusion bodies of hematopoietic tissues. The virus particles are spherical with diameter ranged 50—56nm. Each particle consists of an outer coat appoximately 16nm thick and a core with high electronic density measured 25—30 nm in diameter.