Abstract: BiOI/BiOCl composite photocatalysts with oxygen vacancy (OV) were successfully synthesized by solvothermal method with bamboo charcoal (BC) as the carrier. The effect of temperature and light on the catalytic performance in the removal of NO_x was considered and the photocatalytic reaction mechanism was investigated with the assistance of SEM, XPS, XRD, PL and Uv-vis analysis. The results indicated that optimum denitrification efficiency of 73% can be achieved under 30℃ and with a xenon lamp of 500 W. After the modification with the OV agents, the specific surface area and pore capacity of BC were greatly enhanced; the adsorption capacity was also improved and the functional groups of C=O and -COO can be efficiently broken into C-O functional groups. Meanwhile, the modification with OV agents can increase the photocatalytically active sites, reduce the recombination rate of electron hole pairs, and thus improve the efficiency of NO photocatalytic degradation.