Abstract: The bio-char prepared in a drop-tube furnace was studied under fast pyrolysis conditions, while its pyrolysis properties and microscopic features were analyzed by nitrogen adsorption-desorption instrument and Fourier transform infrared spectrometer. Combined with the adsorption kinetic process, the adsorption characteristics and mechanism of elemental mercury by bio-char were further explored. Results show that the adsorption property of mercury by bio-char depends on not only the pore structures but also the surface chemical properties. Because of the particle agglomeration caused by van der Waals force and liquid bridge force during the sedimentation process, the mercury adsorption capacity of bio-char increases with the rise of pyrolysis temperature, while the BET surface area increases and the content of surface functional groups decreases. The chemical adsorption of bio-char prepared at lower pyrolysis temperatures plays a dominant role in the adsorption process, and with the rise of pyrolysis temperatures, the chemical adsorption weakens, while the physical adsorption improves.