Abstract: This experiment was conducted to explore the complicated tumor manifestation of avian leucosis subgroup J. On the basis of epidemiology survey of four Qingyuan local layer chicken farms in Guangdong province, then the avian leucosis virus was isolated and detected by PCR test, and avian leucosis virus subgroup J (ALVJ) was definite diagnosed as the pathogen. The histopathologic study showed that the most tumorous manifestation was lymphocytic leucosis (82.9%), and then was hemangioma (11.4%), myeloid leukosis was 5.7%. Abnormal proliferation of lymphocytic leukosis was occurred mainly in parenchymatous organs, including heavy swollen of liver, spleen, kidney, lung, proventriculus and pancreas. There were many ivorywhite tumors and nodules occurred in the parenchyma, and the sections were homogeneous and soft. The solid components of tumors were typical lymphoblast and neoplastic lymphoid cells, and many phanerous pathologic nuclear mitotic figures were observed. Those results confirmed that there appeared a novel tumorous manifestation in Qingyuan local chicken, lymphocytic subgroup Javian leukosis.