The invention belongs to the technical field of environmental protection materials, and particularly relates to an organic dye degradation catalyst-bismuth pentachloride.benzylpyridium quaternary ammonium salt, the molecular structure is shown as formula I, and the organic dye degradation catalyst can be used for rapidly degrading rhodamine B (RHB) and methylene blue (MB) under dark conditions. Acertain amount of CdS loaded on the organic dye degradation catalyst can form a new photocatalytic composite material, can completely degrade RHB and MB under natural light, and has good cycle degradation efficiency. The invention further discloses preparation methods of the organic dye degradation catalyst and composite catalytic material.