Abstract: The lymphatic organ of shrimp Penaeus chinensis and the cultured lymphatic tissues fromfarmed and wild shrimps were examined under the transmission electronic microscope (TEM). The particles with envelope , which are icosahedron in shape and 136 nm in diameter , were found in the cytoplasm in all samples .It seemed to be the Iridovirus .Another virus was found in the cytoplasm of lymphatic tissue of farmed shrimp .The particles were icosahedron , 33 nm in diameter and without envelope , which seemed to be the Picornavirus .No significant replication of the viruses was found in the cultured cells .Pathological changes , including karyorrhexis , nuclear hypertrophy , cytoplasm vacuolization , tissues necrosis of lymphatic organ were also observed .