Abstract: UDP-glucose: flavonoid 3-O-glucosyltransferase (UF3GT) uses flavones, dihydroflavonol or anthocyanin as the acceptor and uridine 5′-diphosphate-sugar as the donor to catalyze the production of flavonoid 3-O-glycoside compounds. Based on sequence homology and transcriptome data, we screened and cloned a UF3GT gene named CtUF3GT (GenBank No. OM948976) from safflower. Biological information analysis demonstrate that CtUF3GT has highly conserved PSPG motif. The open reading frame of CtUF3GT is 1 446 bp, encoding 481 amino acids, with a presumed molecular weight of 52.36 kD and a theoretical isoelectric point of 5.33. Multiple sequence alignment indicate that CtUF3GT has a high homology with UF3GT from Asteraceae, and phylogenetic analysis showed that CtUF3GT clusters with functional identified UF3GTs from other species. The purified recombinant protein glucosylated kaempferol and quercetin to biosynthesis of kaempferol 3-O-glucoside and quercetin 3-O-glucoside, respectively. And CtUF3GT prefered to use kaempferol as substrate. qRT-PCR analysis showed that the UF3GT gene was most highly expressed in flowers, followed by leaves, with very low expression in bracts and stems, and no expression in roots. The expression of UF3GT gene showed a trend of increasing and then decreasing at different stages of flower development. The expression of CtUF3GT gene in safflower with different flower color was highly significant (P < 0.01) at S1, S2, S5, S6 and S7 stages of flower development, in which the expression of CtUF3GT in white safflower was 5.3 and 3.1 times higher than that in red safflower at S6 and S7 stages. This study lays the foundation for further exploring the role of CtUF3GT in the mechanism of safflower flavonoid secondary metabolite biosynthesis and accumulation.