The invention relates to a defluorination biological adsorbent made by tea residue modification, a preparation method and application thereof. The preparation method includes: firstly removing soluble pigments and other substances from tea residue by sulfuric acid to obtain to-be-modified tea residue, then immersing the to-be-modified tea residue in a mixed solution of aluminum, iron, zirconium, rare earth, titanium and other metal ions, loading the generated hydroxide in tea residue under an alkaline condition, then performing high temperature drying to ensure that the hydroxide is fully loaded in the tea residue, and finally carrying out washing and drying to obtain the defluorination biological adsorbent. The main raw material of the biological adsorbent is tea residue, and has wide source and low price. The defluorination biological adsorbent provided by the invention not only eliminates tea residue waste and the pollution caused thereby, but also provides a new way for high value utilization of tea residue, and solves the problem of difficult treatment of tea residue in the industrial production process. The preparation process of the biological adsorbent provided by the invention has the characteristics of mild reaction conditions, simple and practicable process route and easy industrial operation, and has the potential of large-scale popularization and application.