Alanine aminotransferase (AlaAT) is a pyridoxal5′phosphatedependent (PLP) enzyme which plays a critical role in linking carbon and nitrogen metabolism. AlaAT is also involved in plant responses to abiotic stress. In this study, based on the transcriptome data of tea plant, we cloned CsAlaAT gene encoding alanine aminotransferase from cDNA of ‘Huangjinya’ by RTPCR method. In addition, the expression profiles of the CsAlaAT gene in different tissues and under extreme temperatures and hormone treatments in two tea plant varieties (‘Huangjinya’ and ‘Yingshuang’) were analyzed by quantitative real time PCR. Results showed that the length of open reading frame (ORF) of CsAlaAT gene was 1 662 bp, encoding 553 amino acids. CsAlaAT contains typical conserved AATlike domain which belongs to Aspartate aminotransferase family. Multiple alignments of CsAlaAT with related plant species showed that the identity of them was 78.83%. The PLP binding sites and the catalytic residue of 358 Lys were highly conserved. The CsAlaAT is hydrophilic protein. Its theoretical relative molecular weight is 60 877.5 D. Theoretical isoelectric point is 6.11. Percentages of basic, acidic, aliphatic and aromatic amino acids were 12%, 11%, 22% and 8%, respectively. A threedimension crystal structure of CsAlaAT was established on the basis of the HvAlaAT which share identity of 78.38% with CsAlaAT. Quantitative realtime PCR analysis of the expression profiles showed that the CsAlaAT gene was tissuespecific expressed in two tea plant varieties ‘Huangjinya’ and ‘Yingshuang’. The highest expression level was found in the root. The CsAlaAT gene could respond to high temperature (38 ℃) and low temperature (4 ℃) treatments. Exogenous application of abscisic acid (ABA) and gibberellins (GA) could downregulated the CsAlaAT.