Abstract: The pot culture containing upland red soil from Longyou, Zhejiang province and Hoagland nutrient solution culture were conducted to study the role of silicon and its possible mechanism in reducing Al toxicity to barley crop Equal amounts of N, P, K were added to the soil with varying silicon levels (Si 0.0, 0.10, 0.20 g/kg) Total Al in the solution was 13.5 mg/L with a Si/Al ratio of 0.0, 0.5, 1.0, respecitively Barley seedlings were harvested and analyzed Results indicated that the average height, dry matter of shoots and roots of barley seedlings increased significantly after treatments of silicon Silicon caused Al to accumulate in the roots and promoted phosphorus to be transferred to the shoots The results suggested that silicon alleviated Al toxicity to barley by forming soluble, less toxic hydroxyalumino silicate (HAS) ions in the soil and nutrient solution, thus reducing the concentration of toxic Al species, and by redistributing Al and P in the shoots and roots