To investigate the gene structure, characteristics and potential biological function of uridine diphosphate glucose dehydrogenase 6gene (UGD6) in Dimocarpus longan Lour. (longan), we cloned the key gene DlUGD6 of polysaccharide synthesis in longan by RTPCR and RACEPCR. Its bioinformatics, subcellular localization and expression patterns in somatic embryogenesis, embryonic deveploment and different tissues were also analyzed. The results showed that: (1)the cDNA length of DlUGD6 was 1 860 bp, which contained an open reading frame of 1 443 bp and encoded 480 amino acids (GenBank accession number KU198438). Bioinformatics analysis showed that DlUGD6 belonged to the family of UDPglucose/GDPmannose dehydrogenase, which had three typical conserved domains. According to phylogenetic tree analysis, DlUGD6 kept close genetic relationship with Citrus sinensis. (2)Observation of fluorescence localization by GFP in onion epidermis indicated that DlUGD6 was localized in cytoplasm. The results of qRTPCR indicated that DlUGD6 was upexpressed in nonembryogenic callus and it kept stable in other stages of somatic embryogenesis in longan. The expression level of DlUGD6 in S3 and S7 stages of embryo development was the highest. In addition, the expression of DlUGD6 kept the highest in anther and stem of longan; As a whole, it was higher in genital organs than that in vegetative organs. These results suggested that DlUGD6 might involve in synthesis of cell wall polysaccharides in growth and development of longan.