Developing new type of environmental purification materials and antibacterial materials is of great significance. Herein, a novel cotton fiber (CF) based composite CF@ZIF-8 was designed by in-situ growth strategy and was applied in the photocatalytic degradation and antibacterial. Reactive Black KN-B (RB5) was used as a model pollutant. The results showed that the photocatalytic degradation of RB5 was well fitted by the first-order kinetic model and the degradation rate of RB5 solution (20 mg/L) was approximately 89% under visible-light irradiation within 180 min. In addtion, the CF@ZIF-8 composites showed well antibacterial activity against Escherichia coli and Staphylococcus aureus with a bacterial reduction rate exceeding 98%.