Three common agricultural wastes,including reed stalk,cassava stalk,and rice plant stalk were used to prepare reed stalk biochar (RESB),cassava stalk biochar (CSB) and rice straw biochar (RISB) by oxygen pyrolysis at lower limit at medium-high temperature.The physico-chemical characteristics and surface morphology of the three different biochars were determined.At the same time,the adsorption capacity of the three biochars on four common heavy metal elements (Cr,Ni,Cu and Zn) from tailings leaching solutions were investigated under different adsorption time.The results showed that at the same magnification,CSB has the largest pore size and is closely arranged,while RESB has the least number of holes;the number of active adsorption sites and stable carbon oxygen complexes on the surface of RISB is less than that of CSB and RESB,and it has stronger hydrophobicity;for Cr,Ni and Cu,CSB has the potentials to be adsorbent while for Zn,RISB has higher adsorption and removal efficiency.