Abstract: Nine-year-old ‘Summer Black’ grapes were used as the test materials, using the method of spraying the foliage as well as the fruit surface of ‘Summer Black’ grapes using multi-walled carbon nanotubes（MWCNTs）,with four treatments of 0 mg·L^-1（CK）,4 mg·L^-1（M1）,8 mg·L^-1（M2）,and 12 mg·L^-1（M3） MWCNTs in four treatments.The effects of MWCNTs on the fruit quality of ‘Summer Black’ grapes were investigated, and the optimal concentration of MWCNTs to improve the fruit quality of ‘Summer Black’ grapes was screened, in order to provide reference for the application of nanomaterials in grape production.The results showed that MWCNTs significantly increased grapevine fruit quality and longitudinal diameter.At the 35^th day after treatment, fruit color index（CIRG）,solid-acid ratio, anthocyanin content, PAL and CHI activity were higher in M1,M2 and M3 treatments than in CK,and pericarp chlorophyll content and titratable acid content were lower than in CK.At the 35^th day after treatment, fruit color index, soluble solids content, pH, solid-acid ratio, anthocyanin content, PAL enzyme activity, and CHI enzyme activity were all significantly higher in the M2 treatment than in CK,being 7.7%,5.9%,3.8%,26.6%,19.7%,25.22%,and 16.55% higher, respectively, than in CK.Also titratable acid content and chlorophyll content were lower than CK,16% and 16% lower than CK,respectively.The composite score indicated that M2＞M1＞M3＞CK.Spraying ‘Summer Black’ grapes with 8 mg·L^-1 MWCNTs（M2） had the best effect on their overall quality improvement.