Based on a 490 bp middle segment of K ion channel gene, a pair of specific primers was designed to acquire 5' and 3'-ends of cDNA by RACE strategy. An unreported K ion channel gene in tobacco (Nicotiana tabacum) named as NKT5 was obtained by splicing three cDNA sequences and sequencing full-length cloning. The full-length cDNA of NKT5 is 2 365 bp long with 190 bp 5'-untranslated region (UTR), 249 bp 3'-UTR and 1 926 bp coding sequence. The deduced amino acid is 641 AA long. The gene sequence analysis and function prediction were carried out in order to clarify molecular mechanisms of potassium absorption and stress-resistance in the tobacco.