The bursa of Fabricius, the central humoral immune organ unique to birds, plays an important role in B-lymphocyte differentiation. In order to gain a better understanding of the molecular mechanism of critical biological processes like B-cell immigration, differentiation, and final emigration, the transcriptional changes during embryonic and posthatch development of this organ were investigated. We generated a cDNA library from total RNA isolated from 3 representative developmental stages (embryonic day [ED] 10, posthatch d 2 and d 21). We generated over 70 million high-quality reads from the cDNA library by using deep sequencing. The uniquely mapped sequences of ED 10, d 2 and d 21 were 71087280, 59167491 and 70263675 respectively. All of the differential expressed genes were involved in Vitamin A metabolism, regulation of actin cytoskeleton, Wnt signaling pathway, MAPK signaling pathway, Jak-STAT signaling pathway, Notch signaling pathway, Toll-like receptor signaling pathway. The RNA-seq analysis provides a powerful method for analyzing the transcriptome and investigating the transcriptional changes of different development stages of bursa of Fabricius. The assembled bursa transcriptome provides an essential resource for future investigations about chicken Bursa development.