Aluminum toxicity has been a serious agricultural problem in acid soils, so the study of physiological response of plants to aluminum stress is of great significance. In this research, five physiological indices of buckwheat in acid-aluminum stress were investigated. Buckwheat was cultured in sand which was treated by different concentrations of aluminum (0,10,100,1 000 mg/L) and pH value(3,4,5). At 14d and 28d after buckwheat sprouting, roots and leaves were used to probe into the changes of physiological characteristics. The result indicated that under acid-aluminum stress, even in10mg/L pH5, the cells of both root and leaf were damaged and the growth of buckwheat was influenced. With the rise of aluminum concentration or with the drop of pH, the root system activity (RA) was decreased, the membrane permeability of root cells (MP),the amount of malonaldehyde (MDA) and free proline (Pro) in leaves were increased, and the activity of peroxidase (POD) was raised. Especially 1 000 mg/L pH3, the cells of buckwheat were destroyed worst. The membrane permeability of root cells was 2.59 times and the amount of malonaldehyde in leaves was 3.78 times than the control at 14d after sprouting, 2.10 times and 1.95 times at 28 d. These physiological indices of buckwheat had significant correlation with each other under acid-aluminum stress. Aluminum toxicity became less in its growth.