The surface properties and structural characteristics of humic acid, as an adsorbent, were characterized by elemental analysis, scanning electron microscope (SEM), and Fourier-transform infrared spectroscopy (FTIR), the adsorption characteristics and mechanisms of humic acid on Se(Ⅳ) was explored through the analysis of adsorption kinetics, adsorption isotherm, external conditions on the adsorption of humic acid on Se(Ⅳ) and desorption characteristics. The results show that high degree of humification and large surface area of humic acid could offer more binding sites. The adsorption capacity of humic acid on Se(Ⅳ) is increased with the decrease of pH, and the increase of Se(Ⅳ) initial concentration and humic acid content. Furthermore, the adsorption of Se(Ⅳ) by humic acid is mainly occurred in the first 15 minutes, and the adsorption process could be described by the quasi second-order kinetic equation; adsorption isotherm data is fitted the Freundlich model. FTIR spectra reveal that C=O, C-O, C=C, O-H and N-H are possibly involved in the binding process as the main functional groups, and the major mechanism of humic acid adsorption for Se(Ⅳ) is electrostatic attraction and ligand exchange.