Ultraviolet photodegradation (UV) was utilized as a pretreatment to enhance the biofiltration process (BF and BTF) for the removal of hydrophobic α-pinene. Based on the experimental data, the mass transfer behavior and microbial activity were analyzed by the theoretical models. The gas phase saturated constant K m of α-pinene was 1.0 g m -3 in the UV-BTF, 20 times than that in the sole BTF; while this value in the sole BF was slightly higher than that in the UV-BF. Fitted by the Ottengraf-van den Oever model, the critical inlet concentration in the UV-BTF was 555.22 mg m -3 , which was much higher than that in other systems. Through the analysis of microbial activity and specific oxygen utilization rate, the biofilm in the UV-BTF was much more active, and the maximum specific oxygen utilization rates for α-pinene and its photodegradation intermediates were respectively 1.16, 0.34, 0.41and 0.25 mgO 2 mg -1 DW h -1 , slightly higher than 150%–200% of the values in other systems. Such results illustrated that UV photodegradation could reduce the mass transfer inhibition for α-pinene and simulate the growths of microorganisms in the subsequent BTF, thus enhancing the overall removal capabilities. But the UV technology was not a suitable pretreatment for the subsequent BF owing to BF’s own characteristics and cumulative toxic effects of ozone.