The invention discloses a biomass adsorbent capable of being regenerated by illumination as well as a preparation method and application of the biomass adsorbent. The preparation process comprises thefollowing steps: (1) designing a photosensitive functional monomer; (2) preparing a biomass macromolecular initiator; and (3) preparing the biomass adsorbent capable of being regenerated by illumination. The biomass adsorbent prepared by the method disclosed by the invention is rich in raw material sources, green and environment-friendly, can be used for photo-responsive adsorption and release ofvarious pollutants (such as heavy metals and organic matters) in the environment; desorption of the pollutants and regeneration of the biomass adsorbent can be realized under a controllable illumination condition, the defects that a traditional adsorbent regeneration process is complex, secondary pollution is easy to generate, the repeated utilization rate of the adsorbent is low and the like areeffectively overcome, and the biomass adsorbent has a wide application prospect.