The common food preservative Potassium sorbate was used as control on the study of Natamycin on Botrytis cinerea virulence and preservation of postharvest grapes.The inhibitory activity of Botrytis cinerea hyphae growth in antibacterial liquids with different concentrations was measured to determine its inhibitory virulence.The preharvest grapes were soaked by antibacterial liquid,and then their sensory indicators,inherent quality and metabolic physiology were evaluated to study the inhibitory effect of Natamycin on gray mold after grape harvest respectively.The results showed that the value of EC 50 of Natamycin antibacterial liquid(EC 50 = 433.96 mg / L) was significantly less than that of potassium sorbate preservative solution(EC 50 = 5753.65 mg / L).Compared with the control,treatment with Natamycin before harvest could effectively inhibit the increase of grape mildew and stems browning index.Furthermore,it was better to keep the soluble solids in fruit,titratable acidity and content of Vc,and significantly inhibited the increase of berry breathing strength in late storage,membrane permeability and the increase of MDA.In summary,Natamycin can significantly inhibit in the growth of gray mold after grape harvest and has a bright application prospects in biological preservation field of fresh grapes.