GA signaling transduction pathway or biosynthesis, which is impeded, is an important factor in plant dwarfing. DELLA protein is an important negative regulator in GA signaling transduction pathway. DELLA protein gene, named BsGAI2, was cloned from Buxus sinica var. parvifolia using PCR and RACE techniques. BsGAI2 contains the complete coding region, having 2576bp in full length, contains an opening frame of 1884bp. Real-time quantitative PCR demonstrated that, the amount of BsGAI2 expression was the highest in stem and the lowest in flower from Buxus sinica var. parvifolia. The transgenic tobaccos contains BsGAI2 gene, appearing dwarf, internodes shorter, growing slowly, delay flowering. The transgenic tobaccos were detected by GFP fluorescent methods, whose leaf, stem were founded fluorescent signal, and the stem xylem had bright-enriched signal. These results all indicated that BsGAI2 gene may play an important role in the process of shorting stem internode for Buxus sinica var. parvifolia dwarf. This study analyzed physical & chemical properties and functional identification of BsGAI2 gene encoding protein, which provided the theoretical basis for the further study of BsGAI2 gene and DELLA protein family.