Abstract: To understand the responses of photosynthetic physiology to low light and its performance after regaining normal light，4-year-old‘Khoyo’grapevines were treated with 70% shading for 20 days right after blooming. Characteristics of chlorophyll fluorescence，content of chlorophyll，sugar content and composition， expressions of photosynthetic enzyme genes，and sucrose phosphate synthase（SPS）. Results showed that low light treatment resulted in lower fruit quality and fruit size，reduced photosynthetic rate and efficiency，reduced the synthesis of soluble sugar in leaves. Meanwhile，expressions of photosynthetic enzymes genes and sucrose phosphate synthase genes in leaves also decreased. After regaining normal light，the photosynthetic rate and photosynthetic efficiency increased，and the expression of PRKase，SPS1-2，SPS3 recovered to the level of the control one. After 50 days regaining normal light，the contents of glucose，fructose and sucrose and Chl. a/b in the treatment group were not significantly different from the control. However，the expression of RbcL1 was not restored. It is concluded that the low light treatment could irreversibly affect overall photosynthesis of grapevine leaves，inhibit the expression of photosynthetic enzyme genes and key enzymes of sucrose metabolism genes，resulting in smaller berries and lowering the fruit quality.

Key words: grapevine, low light stress, photosynthesis, gene expression, soluble sugar content