Abstract: In this paper,through pot experiment,we studied the aluminum toxicity of some crops seedling term.The tested soil is the red soil of Quaternary period in southern Hunan.The tested crops are some main crops in red soil dry land.It is found that the plant grows different with the different aluminum application treatment.Under the toxic critical value,a little content of aluminum application can activate the plant growth.When aluminum toxicity,the growth of root systen can be limited.The shoot become slim and dwarf,and the leaf number and leaf become little.The leaf tip of some crops becomes yellow.When toxicity is serious,the plant is dying. The crop's ability of tolerating aluminum toxic critical value is as follows:wheat 4.0coml/kg,maize 4.8cmol/lkg,rape 4.0cmol/kg,soybean 5.2cmol/kg,peanut 4.4cmol/kg. The mechanism of crop aluminum toxicity is analyzed too.At first,the aluminum toxicity hampers root growth.When the high content of aluminum accumulates in the root,the aluminum toxicity will come into being.It will affect absorbing and transporting nutrient and water seriously.Ultimately,it limits the shoot growth.