In this work, the 2D SnS2/g-C3N4 heterojunctions were successfully prepared by heating the homogeneous dispersion of SnS2 nanosheets and g-C3N4 nanosheets using a microwave muffle. SEM, TEM and HRTEM images indicated that the SnS2 nanosheets were loaded on the surface of the g-C3N4 nanosheets. The UV-vis spectra show that the absorption intensity of the as-prepared samples was increased and the absorption range was also extended from 420 nm to approximately 600 nm. The H2 production rate over 5 wt% SnS2/g-C3N4 can reach 972.6 μmol·h-1·g-1 under visible light irradiation (λ > 420 nm) using TEOA as the sacrifice agent and Pt as the electron trap, which is 2.9 and 25.6 times higher than those of the pristine g-C3N4 and SnS2, respectively. According to the obtained PL spectra, photocurrent and EIS spectra, the enhanced performance for H2 generation over the heterojunctions is primarily ascribed to the rapid charge transfer arising from the suitable band gap positions leading to an improved photocatalytic performance. The recycling experiments indicated that the as-prepared composites exhibit good stability in H2 production. Additionally, a possible enhanced mechanism for H2 evolution was deduced based on the results obtained by various characterization techniques.