Abstract: To develop a inactivated vaccine against subgroup B avian leukosis viruses (ALV-B) and determine if vaccination of chicken breeders could protect young chicks from ALV-B horizontal infection at early stage and accelerate eradication progress. Chicken embryo fibroblast (CEF) cells were inoculated with SDAU09C2 strain of ALV-B and ALV-CEF was inactivated for preparation of oil-adjuvant vaccine. Eggs were collected from un-vaccinated and 9 vaccinated great parent female chickens for incubation. One-day-old chicks were bled for testing their maternal antibodies to ALV-A/B and then inoculated with ALV-B. Viremia and cloaca p27 detection dynamics were tested and compared between chick groups with or without maternal antibody to ALV. In 3 weeks after the 3rd vaccination with the inactivated vaccine, all 9 vaccinated breeders developed high antibody titers against ALV-A/B with ELISA read values of 1.69-1.89 (the positive base line was 0.4) and kept at the high titers for at least another 4 weeks. Maternal antibody was detected in 70% (12/17) of chicks from breeders with high antibody titers to ALV-A/B. Only 4 of 12 chickens with maternal antibodies developed temporary viremia and no viremia was detected in the left 8 maternal antibody positive chickens during the whole 14 weeks after inoculation of ALV-B at 1 day of age. But the persistant viremia was detected in 2-8 weeks in all 9 maternal antibody negative chickens and the viremia persisted in the whole tested period of 14 weeks after inoculation of ALV-B. The inactivated ALV-B vaccine could induce high titer antibody reaction to ALV-B, it could provide matarnal antibodies to 1-day-old chickens and protect chickens from early infection of ALV-B.