In this study, according to the results of chestnut (Castanea mollissima Bl.) cDNA library analysis, we obtained the EST sequences of caffeic acid Omethyltransferase (COMT) gene. The fulllength cDNA (CmCOMT) in chestnut was cloned by RTPCR. Analysis of the information of CmCOMT gene encoding protein was carried out and the gene was also expressed in the prokaryotic. The results showed that: (1) CmCOMT gene contains a 1 098 bp open reading frame (ORF) encoding 365 amino acid residues with a calculated molecular weight of 39.6849 kD and theoretical isoelectric point of 5.83, which has the typical characteristics of plant SAMdependent methyltransferase, and GenBank accession number is KU365322. （2）at the nucleotides and amino acids levels, the similarity of the CmCOMT gene to the corresponding sequence in Betula pendula and Betula platyphylla was more than 90%, respectively. Homology modeling showed that the 3D model of CmCOMT was similar with that of alfalfa (Medicago sativa) MsCOMT, suggesting that it might have similar function to MsCOMT. Phylogenetic tree analysis showed that CmCOMT had the same evolutionary ancestry as other plant COMTs, and was closely related to the species of Betulaceae. （3）SDSPAGE analysis showed that the optimal expression condition of CmCOMT protein was 0.3 mmol/L IPTG at 25 ℃ for 6 h, the molecular weight of the protein was about 44 kD, which was mainly in the form of soluble protein. This study laid the foundation for biological function research and application of the key enzyme gene CmCOMT in lignin synthesis pathway.