Abstract: A new cDNA sequence encoding GGPPS (designated as Ntggpps3) from tobacco (Nicotiana tabacum) was cloned by RACE techniques and assayed by bioinformatics. The cDNA sequence of Ntggpps3 was of 1251 bp with an open reading frame (ORF) of 1092 bp encoding 363 amino acids. The protein NtGGPPS3 shared high similarity with other plant GGPPSs. The bioinformatics prediction showed that NtGGPPS3 might be hydrophilic with the molecular weight of 39.5 kD and isoelectric point of 6.28, and its N-terminal presented a chloroplast transit peptide. The secondary structure was mainly composed of helix and random crimps, and tertiary structure contained two classical Asp-rich motifs of GGPPS proteins which were considered as the active sites. A 3-D structure of NtGGPPS3 was constructed through homology-based modeling. Phylogenetic analysis demonstrated that plant's GGPPSs had two branches: one was large subunit and the other was small subunit and NtGGPPS3 belongs in the former.