Abstract: After the successful preparation of PANI/CFs by in situ depositing polyaniline (PANI) onto cellulose fibers (CFs), CdS@PANI/CFs composite was then synthesized via using the high absorption of Cd2+ by PANI/CFs. FT-IR, XRD and SEM-EDX were applied to characterize these composites. It was found that the intervention of PANI significantly promoted the in situ deposition of CdS nanoparticles onto CFs. The as-prepared CdS@PANI/CFs composite was used to degrade methylene blue (MB) under visible light radiation. The degradation ratio of MB by CdS@PANI/CFs was about 1.5 times higher than that by CdS@CFs at the same CdS deposition amount, which indicated PANI had a marked enhancement effect on the visible light photocatalytic degradation of MB. The effects of different process variables, such as MB concentration, catalyst dosage and utilization times, on the degradation ratio of MB were investigated. With increasing the MB concentration, the degradation ratio of MB decreased. The degradation ratios(5 h) were 90.37%, 84.15%, 77.35% and 58.53% when MB concentrations were 10, 15, 20 and 30 mg/L, respectively. The optimum dosage of catalyst was 0.4 g when MB concentration was 20 mg/L and volume was 400 mL. CdS@PANI/CFs composite also exhibited a good reusability after three times of utilization(the degradation ratio of MB was 80.36%).