Objective. The goal of this paper is to investigate the relationship between the N-glycosylation of acetylglucosaminyltransferase V(Glc NAcT-V) and its activity and to know which site among the 6 N-glycosylation sites in the GlcNAcT-V gene is the most important.Methods. Wild type of GlcNAcT-V was transfected into COS-7 cells and its activity was measured 48 h later. The first site (Asn 110) was mutated with site-directed mutagenesis and transfected into COS-7 cells.Results. It was found that after the cells were added tunicamycin(TM, 1 μ g/ml), the activity was 11.7% of the wild type. The activity of the cells with mutating GlcNAcT-V was about 12.0% of the wild type. RT-PCR showed that there was no significant change in mRNA expression among the three groups.Conclusion. The N-glycosylation is important for its activity. Our results suggest that the N-linked carbohydrates on GlcNAcT-V are required for the posttranscriptional activity of the enzyme.