Selenium (Se) and selenoproteins play important roles in the immune system and Se deficiency will affect immune functions in chicken.Dietary Se can influence the expression levels of selenoproteins, however, little is known about the expression patterns of selenoproteins.The aim of the present study was to investigate the effect of dietary Se deficiency on the expressions of 23 selenoproteins in broiler chicken immune organs.In this study, one hundred and fifty broiler chicks (1 day old;Weiwei Co.Ltd., Harbin, China) were randomly divided into two groups (75 chickens per group).The chickens were maintained either on a diet supplemented with Se through the addition of 0.2 mg/kg Se (C group) via sodium selenite or on a Se-deficient granulated 76 diet (L group, from the Sedeficient region of Heilongjiang Province in China, containing 0.008 mg/kg Se) until the broiler chicks exhibited ED onset.Following euthanasia, the samples from the immune tissues (including the spleen, thymus and bursa of Fabricius) were quickly collected, and the mRNA expression levels of 23 selenoproteins were examined by realtime quantitative PCR and analyzed using the way of principal component.The results showed that Se deficiency decreased the mRNA levels of 23 selenoproteins respectively in the thymus, spleen and bursa of Fabricius tissues of broiler chickens in the L groups.Further, we found that the mRNA levels of Dio1 in the thymus, Txnrd2 in the spleen, and Txnrd3 in the bursa of Fabricius decreased mostly among 23 selenoproteins (90.9%, 83.3%, 96.8%).And in addition, principal component analysis (PCA) suggested Gpxs, Txnrds, and Dios families may play crucial roles in chicken immune system.It is well known Gpxs, Txnrds were great concerned with antioxidant.These results indicated that Se deficiency mainly influenced the expressions of antioxidative selenoproteins (Gpxs,Txnrds) in chicken immune organs.And, antioxidative selenoproteins especially Gpxs may play a crucial role in chicken immune system.Thus, it helps us focus on some specific selenoproteins when studying the role of Se in chicken thymus, spleen, and bursa of Fabricius tissues.