Abstract: Pot experiments and chemical analysis were conducted to determine an effect of Al stress on growth of soybean crop.The results showed that there was a significant effect of Al stress on the major agronomic characters of soybean in solution.The critical value of Al toxicity for soybean was 12ppm Al in solution.Under the condition of Al stress,there were negative relationship between the Al concentration and intensity of biological oxidation of α-naphthylamine in the root system,and pos-itive relationship between Al concentration and electrical conductivity and potash content in permeable solution in root systerm.The positive relationship between Al concentration and the content of proline in leaves of soybean could also observed,so the content of proline in leaves can be used as a physiological indicator of Al-torelance of soybean crop.