Metal-organic frameworks (MOFs) are a new type of porous crystal materials that have been widely used in various fields. Owing to their adjustable porous structure, MOF photocatalysts with high catalytic activity have become a research hotspot. In this study, NH2-MIL-125/CoS(x)samples were investigated as a novel visible light-responsive catalyst for the removal of organic dye. The NH2-MIL-125/CoSx-20 composites showed the best photodegradation efficiency, where photodegradation of the rhodamine B reached 95.4% in 45 min. CoS(x)was able to effectively extend the wavelength absorption range of NH2-MIL-125 and effectively separate the photogenerated electrons and holes and that could lead to the improved photocatalytic performance of the composites. The reactive superoxide radical (O-center dot(2-)) was identified as the main active species using reactive species capture experiments, and a reasonable photocatalytic mechanism was proposed. This paper is intended to guide the development of organic-inorganic hybrid materials for environmental remediation.