Abstract: In order to explore the effect of UV-B irradiation time on the fruit quality and flavonoids of Cabernet Sauvignon wine grape, the experiment set up four gradients of UV-B irradiation for 2, 4, 6 and 8 h each day, with no UV-B irradiation as the control (CK). The fruit quality and flavonoids of grapes with different UV-B irradiation time were detected and analyzed. The results showed that short-term UV-B irradiation increased the content of soluble sugar in fruit, and the contents of total phenols, tannins, total flavonoids, flavan-3-ols and total anthocyanins increased under different UV-B irradiation time. Different UV-B irradiation time had a significant effect on flavonoid metabolites in wine grape skin, and 13 differential metabolites were screened out, and 5 substances were significantly up-regulated and 8 substances were significantly down-regulated. Seven differential metabolites were enriched in the flavonoid and secondary metabolite synthesis pathways, accounting for 77.78% of the total metabolites. Comprehensive evaluation of the fruit quality and the measured value of flavonoid products in the peel used principal component analysis. The scores from high to low were UV-B irradiation for 2 h>UV-B irradiation for 8 h>UV-B irradiation for 4 h>UV-B irradiation for 6 h>CK. UV-B irradiation of wine grape Cabernet Sauvignon for 2 h, the fruit quality and flavonoid metabolites were the best.