g-C3N4/SnS2 composites were fabricated by a in situ hydrothermal process. g-C3N4 content was optimized, and the optimal g-C3N4 content is 15%. 15% g-C3N4/SnS2 shows the highest visible-light photocatalytic activity. g-C3N4/SnS2 composites exhibit excellent reusability.