The Sox family of transcription factors is involved in a variety of developmental processes, including sexdetermination and gonadal differentiation. The high-mobility-group (HMG) domains of all Sox proteins have highlyconserved primary structures, and all appear to be capable of binding to the same target DNA sequence ofAACAA(A/T)G. The Sox gene family is divided into 10 subgroups (designated A–J) based on sequence similarity andgene organization. Sox19 is a member of the group B Sox genes, though it differs from other members in possessing anintron. The Sox B group is further divided into the B1 subgroup, which encodes transcriptional activators, and the B2subgroup, which encodes repressors. Based on sequence and phylogenetic analyses, Sox19 has been assigned to the B1subgroup. Interestingly, the Sox19 gene has always been considered fish specific but the full length cDNA encodingSox19 has only been cloned in Danio rerio, Takifugu rubripes, and Dicentrarchus labrax, and little is known about theexpression patterns in other species. In this study, we successfully cloned the full-length Sox19 cDNA sequence of theChinese giant salamander (Andrias davidianus), which is the largest extant amphibian, and used quantitative real-timepolymerase chain reaction (PCR) analysis to detect Sox19 gene expression in different tissues. We cloned a 1290-bpSox19 gene cDNA, including 270 bp of the 5′-untranslated region (UTR) sequence, 858 bp of the open reading frame(ORF), and 162 bp of the 3′-UTR sequence. The ORF encoded 285 amino acids, of which a 71 amino acid protein wasfrom the N-region and a 39–109 amino acid region was the highly conserved HMG-box. Bioinformatics software wasapplied to analyze the A. davidianus Sox19 protein, which is hydrophilic. A subcellular localization analysis showed that96% of the protein was present in the nucleus, possibly without the transmembrane region or signal peptide, 24.91%was in the α-helix, 3.16% was in the extended strand, 2.11% was in the β-corner, and 69.82% was in the random coil.The tertiary structural prediction revealed a α-helical structure as the functional site. The A. davidianus Sox19 proteinencoded 285 amino acids, which is less than that in fish. Therefore, fish have more similar “AAAA” polymers thanthose of the A. davidianus (150 amino acids), but A. davidianus has an additional “QNLV” at the C-terminal end, suggestingthat the Sox19 gene may have lost the lactamine oligomer during evolution and mutated to a more elaborate andcomplex transcriptional regulatory region. The amino acid sequence analysis revealed that the putative A. davidianus-Sox19 protein had 55%, 58%, and 64% identity with T. rubripes, D. rerio, and D. labrax, respectively. The phylogeneticanalysis further demonstrated that A. davidianus split off earlier based on the Sox19 gene data, revealing a more primitiveevolutionary status. The Sox19 gene could have evolved through ancient fish-specific duplication of Sox3, althoughSox19 is expressed in the developing lens and central nervous system. We analyzed Sox19 expression in the gonad,heart, kidney, and bowel of adult A. davidianus to confer the functions of the protein by fluorescence quantitative PCR.The results show the highest Sox19 gene expression level in the heart, suggesting that Sox19 helps maintain heart function.The high expression level in the gonads shows that Sox19 may be involved in gonadal development and differentiation.Sox19 was also expressed in the kidney and intestine, indicating that Sox19 plays a role maintaining kidney andbowel functions in A. davidianus. The Sox19 gene expression levels in A. davidianus were not the same as those in thefish species investigated. Our results provide insight into the role of the Sox19 gene in A. davidianus and further ourunderstanding of Sox19 gene expression in amphibians. The Sox19 gene could be the earliest molecular marker of embryogenesisin A. davidianus.