Cytrochrome P450 are highly potential to detoxify environmental contaminants, but their catalytic systems are too complex to practically apply in industry. In this study, a typical Cytrochrome P450 of CYP119 was coupled with a semiconductor composite of CeO2-3TiO(2), and the photocatalytic property of the coupled system was studied in detail. The samples were characterized by FTIR, XRD, SEM, elemental mapping, DRS, photocurrent, EIS and PL. The results indicate that bare CYP119 enzyme cannot reduce Cr (VI) under light irradiation. But when it coupled with the semiconductor, the coupled system exhibits high photocatalytic reactivity, which is higher than that of bare CeO2-TiO2 and CYP119. The photocatalytic mechanism analysis indicates that the enzyme and the semiconductor are synergistic to function in the coupled system. CYP119 enzyme cannot use light energy directly, but it can be activated by oxidated active species, which are generated by the semiconductor under light irradiation. This study demonstrates that the catalytic activity of P450 enzyme can be triggered by light irradiation. The photocatalytic system is cheaper and more convenient than the classical catalytic systems. The present study exhibits the possibility of P450 to harvest light energy, which is significant to both the theoretical study and practical application of P450 enzymes.