Abstract: In order to study the chemical speciation of typical heavy metal lead in contaminated farmland soil and the response to the amendment by biochar, the BCR three-step sequential extraction was used to the speciation analysis of lead in contaminated soils amended biochar with different application rate during three years (2009-2012), the seasonal variations and stability mechanism was also discussed. Results showed that the pH value and the content of soil organic carbon (SOM) increased by 0.11-0.65 units and 16.0%-51.2%, respectively. Acid dissolved state, reduced state and oxidation state components were significantly reduced and translated to residue state, for example, the three of them decreased by 5.3%-25.0%, 9.8%-22.3% and 40.8%-43.5% in wheat season in 2010, and the residual state increased by 7.8%-16.1%, but different responses in wheat and rice season were also found that the four states concentration were higher in wheat season (2011) than rice season (2010) for the different oxidation-reduction potential due to the different water conditions. The different lead states were significant correlation with soil pH and SOM. Biochar contained large amounts of alkaline material and hydroxyl, carboxyl and organic functional groups, which could fix the varieties, lead effectively by complexation, precipitation, and other chemical mechanisms. It showed that remediation of soils by biochar could effectively reduce the bioavailability and ecotoxicity of lead, and provided a theoretical basis for the amendment of soil polluted by heavy metals.