Abstract: Ninety eight soil samples of 0~20 cm topsoil and 20~40 cm bottomsoil were taken from Chengdu Plain by random method. The contents of Pb in these samples were detected. The Geoaccumulation Index was used to evaluate heavy metal contamination degree. The distributions of polluted soil and the mobility of Pb were discussed. The results show that most of the cropland soil was polluted. Only 20 samples were not polluted among the 86 samples of 0~20 cm topsoil. Among the polluted soil samples, the contamination grade is from 1 to 4, the grade of 1 and 2 is the major one, and they belong to the state of lowmedium and medium contamination grade. Each of the two major grades has 30 soil samples (accounting for 38.4% of the total soil samples) . Few samples has reached intense contamination degree. The distribution of the polluted soil was tightly contacted with the pollution source, and closed to the physical and chemical characters of soil in some degree; Pb was mostly accumulated in 0~20cm topsoil, and mobilized in the soil. The quantity was closed to the physical and chemical characters of the soil.

Key words: Chengdu Plain, cropland soil, Pb pollution, evaluation