Hierarchical network-like graphitic carbon nitride/SnIn4S8 (g-C3N4/SnIn4S8) composites were prepared through a facile low-temperature co-precipitation method. The g-C3N4/SnIn4S8 composite showed enhanced visible-light absorption. The band gap energies of g-C3N4, pure SnIn4S8, and 15 % g-C3N4/SnIn4S8 are 2.58, 1.8, and 1.68 eV, respectively. The photocurrent and photocatalytic activity of the g-C3N4/SnIn4S8 composites firstly increased and then decreased with increasing g-C3N4 content, and it was found that the optimal 15 % g-C3N4/SnIn4S8 exhibited the highest photocurrent intensity and best photocatalytic performance with complete degradation of MO within 80 min under visible-light irradiation, which is much higher than that of pure SnIn4S8. The effect of main reactive species on the MO degradation follows the order of h(+) > O-aEuro cent(2) (-) > (OH)-O-aEuro cent, and the possible degradation mechanism was proposed. Moreover, 15 % g-C3N4/SnIn4S8 exhibits excellent reusability and stability without an obvious decrease of photocatalytic activity after four consecutive photocatalytic degradation-regeneration cycles.