The pollution of water is becoming more and more serious, and photocatalytic degradation of pollutants in water by sunlight plays an important role in the future development. A simple chemical precipitation method was introduced. CNTs were compounded on the surface of Bi₁₂O₁₇Cl₂ to obtain a series of CNTs/Bi₁₂O₁₇Cl₂ composites. The structure, morphology and optical properties were measured and characterized by XRD, TEM, UV?Vis DRS and PL. The results show that compared with single?phase Bi₁₂O₁₇Cl₂, CNTs/Bi₁₂O₁₇Cl₂ composites show excellent pollutant degradation activity and good photocatalytic stability and cycling performance. It is found that superoxide radical (·O {}_{\mathrm{2}}^{-} ) and hole (h⁺) are the main active species through trapping experiments, and the possible degradation reaction mechanism is speculated. This study provides a cheap and simple modification method for improving the photocatalytic performance of the catalyst, and has a certain guiding role in the synthesis of other high efficiency photocatalysts.