Biochar is a novel porous carbonous material derived from pyrolysis of biomass in the partial or total absence of oxygen. In the present study, two biochars were generated from corn straw at pyrolysis temperatures of 350℃and 700℃（referred as BC350 and BC700）, and their structural characteristics were analyzed. The two biochars were investigated for their capacity for Cd（Ⅱ）adsorption from aqueous solution. The degree of aromatic structure, hydrophobicity, pore volume, specific surface area, and porosity of biochars were found higher for BC700. The adsorption of Cd（Ⅱ）onto biochar surface was better described by Two-site Langmuir than by One-site Langmuir adsorption isotherm, suggesting the involvement of multiple adsorption processes. Both ion exchange adsorption and cation-πinteraction were proposed for the adsorption of Cd（Ⅱ）on biochar. Ion exchange mechanism accounted for 13.7% for BC350 and 1.1% for BC700 of total adsorption capacity, respectively; while the corresponding proportion of cation-πinteraction was 86.3% and 98.9%, indicating the leading role of cation-π interaction in Cd（Ⅱ）adsorption. The FTIR spectrograms showed different adsorption sites of aromatic-π structures（for cation-π interaction）and oxygen-containing groups（for ion exchange adsorption）in biochars. The BC700 showed better adsorption performance than BC350 with greater adsorption capacity and lower desorption rate. BC350 was affected by solution pH by a greater extent as compared to BC700, due to the greater proportion of ion exchange adsorption sites.