Abstract: In view of the problems such as the long time of biofilm formation and the low removal efficiency of styrene in a bio-trickling filter, the degradation can be enhanced by the modified method of start-up and the addition of surfactants. To investigate the performance of the horizontal bio-trickling filter at the start-up stage, high-concentration styrene gas-liquid phase combined start-up method was adopted and a small proportion of glucose was added into the nutrient solution. Domesticated compound strains were inoculated. Performance of the horizontal bio-trickling filter was enhanced by adding Tween-80, and its mechanism was studied. Results show that the start-up time of the horizontal bio-trickling filter is only 5 d. When the inlet concentration of styrene is 700-1 100 mg/m³ and the EBRT is 35-40 s, the addition of Tween-80 significantly increases the removal efficiency of styrene by about 10%. Degradation of styrene in the horizontal bio-trickling filter is enhanced in the presence of Tween-80 because the solubility of styrene can be improved in the horizontal bio-trickling filter system, and the content of extracellular polymeric substances and the proportion of dominant bacterial community (Proteobacteria) increases. In addition, the shedding of aging biofilm is accelerated.