has a wide geographical distribution ranging from south-eastern Siberia and Korea through most parts of China to Vietnam. Besides its nutritive and medical value, the turtle also became a model animal for investigating the development and evolution of their unique body and evolution of other biological as well as immune functions. CD3 molecules which are composed of four chains [γ, δ, ε, ζ(η)] act as markers of T lymphocytes and play important roles in T cell signaling, TCR-CD3 complex assembly and T cell mature. To understand its molecular structures, function and evolution in reptile, we cloned the cDNA sequences of CD3γ/δ, CD3ε and CD3 in the Chinese soft-shelled turtle usingthe SMART RACE technology and analyzed its expression pattern in normal and bacterial infected individuals using real time quantitative PCR (rt-qPCR). The deduced CD3γ/δ, CD3ε and CD3ζ encoded 170 aa, 183 aa and 168 aa, respectively. The CD3γ/δ and CD3ε are structurally related with an extracellular immunoglobulin-like domain, a transmembrane region and an ITAM motif containing cytoplasmic tail. The Di-leucine based internalization motif (D¹³⁸RQNLI) and a potential N-glycosylation site (N⁸¹TS) were also found in CD3γ/δ amino acid sequence, and a proline-rich motif (R¹⁵⁵PPPVP) and ER rention motif (Y¹⁷⁵AGLDSR) were found in CD3ε amino acid sequence with the absence of the potential N-glycosylation site. The deduced CD3ζ amino acid sequence has a different structure with a 10 aa extracellular part, a transmembrane region and three ITAM motifs containing cytoplasmic tail. The phylogenetic tree showed that each chain was clustered together and Chinese soft-shelled turtle had a closer relationship with birds and amphibians. Bioinformatics analysis in genomic sequences showed that CD3γ/δ gene, containing 6 exons and 5 introns, and CD3ε gene, containing 7 exons and 6 introns located and transcribed oppositely in the Chromosome Scaffold JH208224 and CD3ζ gene, containing 8 exons and 7 introns with a big intron 1 (66.3 kB) located in Chromosome Scaffold JH209116.1. These conserved motifs in amino acid sequence and genomic arrangement suggested they were conserved in evolution. Real time quantitative PCR results showed that CD3γ/δ, CD3ε and CD3ζ were highly expressed in spleen, liver, intestine and blood, with lower expression level in thymus, kidney, heart, muscle and lung. However, obviously increased expression of CD3γ/δ (69.3 fold), CD3ε (85.7 fold) and CD3ζ (163.4 fold) were observed in thymus at 12 h after the challenge with , indicating an immune response involving CD3 T cells after bacterial infection. This obtained information will provide an important basis for T lymphocyte function analysis in Chinese soft-shelled turtle.