Abstract: In order to reveal the characteristics and functions of GGPPS(Geranylgeranyl pyrophosphate synthase) gene family in tobacco,the GGPPS family in Nicotiana tabacum(N.tabacum),Nicotiana sylvestris(N.sylvestris) and Nicotiana tomentosiformis(N.tomentosiformis) were searched,identified and analyzed in whole genome level through in silico methods.Nine members(seven large subunits and two small subunits) in N.tabacum,and five ones(four large subunits and one small subunit) in N.sylvestris and N.tomentosiformis were identified respectively.The open reading frames of GGPPS were 999-1 119 bp in length,coded 333-372 amino acids with protein molecular weights of 36.3-40.7 kDa and pI in the range of 5.41-8.32.Small subunit genes consisted of two exons,while there was only one exon in large subunit genes.Both genes comprised DD(XX)_1-2D and CXXXC conservative motifs,though certain differences existed.In the course of evolution,GGPPS family in tobacco might have undergone both tandem duplication and segmental duplication,and gene loss event probably occurred in N.tabacum.In addition,NtabGGPPS1-1 and NtabGGPPS1-2 evolved faster than the other ones and might be under purifying selection.