Abstract: To clarify the subcellular localization of chicken bromodomain and extra terminal（BET） family proteins and the expression characteristics of the genes in immune organs, and to provide a basis for the follow-up research on the mechanism of BET family proteins regulating chicken related virus replication, The constructed recombinant eukaryotic expression vectors pEGFP-BRD2, pEGFP-BRD3 and pEGFP-BRD4 of chicken BRD2, BRD3 and BRD4 gene were transfected into human（Homo sapiens） embryonic kidney cells（HEK-293T） in this study, respectively. Western blotting and fluorescence observation were used to detect the expression of BRD2, BRD3 and BRD4 gene and the subcellular localization of chicken BET family proteins. In addition, real time quantitative PCR was used to detect the expression of BRD2, BRD3 and BRD4 gene in immune organs of 1 to 6 months old chickens. The results showed that the chicken BET family fusion proteins EGFP-BRD2, EGFP-BRD3 and EGFP-BRD4 were correctly expressed in cells, and the chicken BRD2, BRD3 and BRD4 were mainly localized in the nucleus. Real time quantitative PCR detection results showed that the BRD2 gene was the most highly expressed in the spleen and thymus of 3 months old chickens and in the bursa of fabricius of 4 months old chickens, with an “inverted V” expression pattern. The expression of BRD3 gene was the highest in the spleen of 1 month old chickens, and BRD3 and BRD4 genes were the highest in the thymus and bursa of fabricius of 6 months old chickens. Among them, the expression of BRD3 gene in the thymus and bursa of fabricius and BRD4 gene in the bursa of fabricius increased gradually in a “straight line” type, and the expression of BRD3 gene in the spleen of 1 month old chickens and BRD4 gene in the thymus were “inverted N” type. The expression of BRD4 gene was the highest in the spleen of 3 months old chickens, and the expression of BRD4 gene first increased and then decreased. Chicken BET family proteins are mainly located in the nucleus, and their genes were expressed in the spleen, thymus and bursa of fabricius of chickens of different ages, but the level of expression showed different trends.