The invention discloses a biological deodorant and a preparation method thereof. The biological deodorant is prepared from the following raw materials: biological enzyme, anaerobic flora, aerobic flora, a plant extracting solution, an enzyme solution, a purification factor, volcanic mud, titanium dioxide fiber, acidic silicon dioxide sol, diisopropyl azodicarboxylate and a noble metal active component. The biological deodorant has the advantages that the deodorizing time is long for foul smells of livestock and poultry farms, sewage around the farms, municipal sewage, wasteyards, sludge and the like, the removal efficiency is high, the effect returns quickly, the removal effect is comprehensive and thorough, various odor-causing substances can be purified and absorbed, mosquitoes and fliescan be repelled to resist and inhibit bacteria; meanwhile, formaldehyde, methylbenzene and TVOC emitted by wastewater discharged from places such as organic synthesis, synthetic fibers, dyes and woodprocessing can be removed and purified to a certain extent, and harm to human bodies can be reduced.