[en] Highlights: • Chloroperoxidase(CPO)-TiO₂ composite combines enzyme and photo catalysis in one pot. A chloroperoxidase (CPO) -TiO₂ thin film type enzyme reactor was constructed by single chloroperoxidase molecule immobilization on TiO₂ mesoporous thin film. The CPO-TiO₂ enzyme reactor showed an enzymatic-photocatalytic synergetic effect, 1 + 1 > 2, when applied in the decolorization of azo dye crocein orange G. Moreover, the enzyme reactor made it possible that the photocatalytic catalysis was carried out under natural sunlight instead of ultraviolet radiation. The synergetic effect was studied by PL emission spectroscopy with terephthalic acid used as a probe molecule to investigate the formation of ·OH radicals. The mesoporous TiO₂, prepared by a sol-gel and dip-coating method, being spherical form without interconnectivity in a 3D pore systems of 8 nm ~ 15 nm pore size, matched the size of CPO molecules. Such an architecture was suitable for single CPO molecule immobilization, which enabled easy access of the substrates to enzyme active sites. The CPO-TiO₂ enzyme reactor was very efficient. 98.61% decolorization efficiency of crocein orange G was achieved in 5 min. It can be reused for seven cycles with no loss in activity. Compared with free CPO, the stability of CPO-TiO₂ enzyme reactor against thermal denaturation and deactivation by high concentration of oxidants or in a strong acid-base environment was enhanced.