Abstract: In order to understand the effects of soil drought on the accumulation of flavanols and the expression of leucoanthocyanidin reductase（LAR），the key enzyme of the flavanols biosynthesis in flavonoid biosynthesis pathway，5 years old grapevines（Vitis vinifera L.‘Cabernet Sauvignon’）were used as materials，and the soil drought was simulated during grape berry development by the controlling irrigation through the prevent-rain shelter and root-cutting groove. The results showed that the single berry weight，longitudinal and horizontal diameter were decrease，and the growth of grape berry was significantly inhibited by soil drought，which indicated that the prevent-rain shelter and root cutting groove were the effective measures to simulate soil drought. In addition，the accumulation of flavanols in grape berry during its development was induced by soil drought was also observed，especially in the young berry. Real-time PCR and Western blot results showed that the soil drought could induce the expression of VvLAR1，VvLAR2，the synthesis of LAR new protein，and increased the LAR enzyme activity，which resulted in the accumulation of flavanols in grape berry.

Key words: grape, berry, soil drought, flavanols, LAR