Abstract: In order to explore the biological function of cyclin-dependent kinase (CDK) in Nicotiana tabacum, the EST sequence of CDK gene in tobacco were obtained by homology search. A CDK gene was cloned from cv. Honghuadajinyuan by RT-PCR and named as NtCDK8. The full length of cDNA encoding zone of NtCDK8 was 1422 bp, which encoded 473 amino acids. The results of amino acid sequence homology analysis indicated that the similarities of NtCDK8 protein with the CDK in Solanum lycopersicum, Solanum tuberosum and Arabidopsis thaliana were 93.02%, 94.08% and 75.32%, respectively. The prediction analysis of protein structure revealed that there was a Serine/Threonine protein kinase domain in NtCDK8 protein, the domain probably promoted the signal transferring from outside to inside of cells via furthering the phosphorylation of residues of serine or threonine in downstream proteins. The comprehensive prediction analysis of hydrophobicity, signal peptide and subcellular localization indicated that NtCDK8 protein might be a hydrophilic protein functioning in nucleus.