AIM To establish a cell line CHL UDP glucuronosyltransferase gene (UDPGT1A9) which will stably express human UDPGT1A9 protein and determine the activity of expressed UDPGT1A9 in drug glucuronidation. METHODS Complimentary DNA (cDNA) of human UDPGT1A9 was subcloned from pREP9 UDPGT1A9 into the mammalian expression vector pcDNA3.1 with DNA subclone techniques. Recombinant expression plasmid pcDNA3.1 UDPGT1A9 was constructed and transfected into Chinese hamster lung (CHL) cells. G418 was used to select transfected clones. The activity and kinetic parameters of expressed UDPGT1A9 were measured using kaempferol as substrate by HPLC. RESULTS The CHL UDPGT1A9 transgenic cell line was established. With kaempferol as the substrate, the enzyme activity of UDPGT1A9 expressed in CHL UDPGT1A9 transgenic cell line was(1.02± 0.11 )μmol·min -1 ·g -1 protein, whereas the native UDPGT1A9 activity was not detectable in control CHL cells. CONCLUSION The CHL UDPGT1A9 transgenic cell line established in this study expressed human UDPGT1A9 protein and had metabolic activity to kaempferol.