Abstract: Myeloblastosis and hemangioma cases associated with avian leukosis virus subgroup J (ALV-J) were first diagnosed in a layer chicken flock in Shandong province on July 2007. The CEFs inoculated by virus extracted from liver were cultured, and detected by indirect immunofluorescence with ALV-J monoclonal antibody G2-3, the results were intense positive. The four isolated strains were named as WS0701, WS0702, WS0703 and WS0704. A pair of primers P1 /P2 was designed according to the sequence of prototype ALV-J HPRS103. DNA extracted from the positive CEFs were selected as PCR template, and a 924 bp fragment was amplified. PCR products were sequenced and demonstrated differ from 95.0% to 97.5% identity with ALV-J HPRS-103. The identity ranged from 92.0% to 95.9% among the four strains and other Chinese field strains. Genetic and antigenic analysis showed the identity of ALV-J which characterized myeloblastic and angiomatous is being more close to HPRS-103 strain than other Chinese filed strains. It indicated that the replication of ALV-J has shown atavism in commercial layer chicken during the several years, and the disease caused by ALV-J showed novel oncology character.