Abstract：Buckwheat husk Biochar （BBC） was prepared and characterized by XRD， Raman， N2 adsorption/desorption， FTIR and XPS analysis methods. Its adsorption performance and mechanism for Ornidazole （ONZ） were investigated in detail. The results showed that BBC carbon yield achieved 24.5%~34.0% when the pyrolysis temperature was in range of 400~800 ℃. The aromaticity， stability （H/C decreased from 0.047 to 0.013）， specific surface area and pore volume of BBC increased with pyrolysis temperature， and the faster and higher adsorption effect was exhibited for ONZ. In addition， the pseudo-second-order kinetic model can well describe the adsorption process， indicating it a more complicated interaction. Langmuir model well fitted the adsorption isotherm， showing that BBC mainly removes ONZ by monolayer adsorption. BBC-800 exhibited the best adsorption removal for ONZ， with the maximum adsorption capacity of 27.12 mg?g-1 calculated by Langmuir model. The pH value had little effect on ONZ adsorption in range of 3.02~11.03. Coexisting ions such as Na+、NH4+、CO32-、HCO3- and SO42- improved ONZ adsorption a little. Humic Acid inhibited the process with ONZ adsorption rate decreasing from 97.15% to 56.86%. Together with the FTIR， N2 adsorption/desorption and XPS analysis， it was speculated that the adsorption mechanism should be attributed to the pore-filling effect， hydrogen bonding， π-π and p-π conjugation between BBC surface and ONZ molecule. The excellent performance of BBC-800 made it remove ONZ residual effectively from the sedimentation tank and lake water. BBC-800 still had good regeneration performance， with the adsorption capacity remaining 14.10 mg?g-1 after three adsorption -desorption cycle. The results are of great significance for the utilization of buckwheat husk and the removal of ONZ residual from water.