As an important regulator in growth, development, and metabolic activities of plant, light is perceived by a variety of photoreceptors that control developmental processes, such as germination, photomorphogenesis, flowering, and senescence. Phytochromes play a pivotal role in plant adaptability to ambient environment. AtPhyB has been found to be involved in the response to red light. At present, PhyB genes have been cloned in various plants, and the expression patterns and functions of the gene family have been studied in Arabidopsis thaliana, rice (Oryza sativa L.), and maize (Zea mays L.), but not in wheat (Triticum aestivum L.). The objectives of this study were to clone the full length of PhyB and study its structure and expression under different lights. The full-length cDNA sequence of PhyB, encoding the apoproteinof phytochrome B, was cloned from wheat cultivar Chinese Spring. This gene is located on chromosome 4D and designated TaPhyB3. This gene possesses four extrons and three introns and the open reading frame TaPhyB3 is 3 501 bases in length, which encodes predicted protein of 1 166 amino acids. The conserved domains of PhyB gene family, i.e., DAF-DOMAIN, PHYTOCHROME REGION, PAS-A DOMAIN, PAS-B DOMAIN, HISTIDINE RELATED DOMAIN 1, and HISTIDINE RELATED DOMAIN 2, were also observed in the predicted protein sequence. The alignment analysis of amino acid sequence showed that TaPhyB3 shared 93% or 90% identity with the PHYBs of rice or maize, respectively, but only 73% with that of Arabidopsis. After treated with continuous darkness, far-red, red, blue, and white lights for 7 d, young seedlings of Chinese Spring were sampled for TaPhyB3 expression analysis using real-time reverse transcription polymerase chain reaction (RT-PCR). TaPhyB3 expression levels in the wheat seedlings under far-red, red, blue, and white lights were 2.2, 7.7, 7.4, and 37.3 times as high as that in seedlings under darkness. When exposed to white light for 90 d, the TaPhyB3 expression was detected in root, stem, leaf, and spike. However, the gene was mainly expressed in above-ground organs of wheat seedling, and TaPhyB3 expression level in leaf was 11.4 times as high as that in root. The expression level of TaPhyB3 is speculated to positively correlate with the degree of the seedling photomorphogenesis.