Although graphitic carbon nitride (g-C3N4) is an attractive photocatalyst for solar H-2 generation, the preparation of g-C3N4 nanosheets via a "green" and simple method as well as the construction of highly-efficient g-C3N4-based photocatalysts are still challenges. In this study, g-C3N4 nanosheets prepared by a simple probe sonication assisted liquid exfoliation method were used to construct 2D-2D MoS2/g-C3N4 photocatalyst for photocatalytic H-2 production. The 2D-2D MoS2/g-C3N4 photocatalyst containing 0.75% MoS2 showed the highest H-2 evolution rate of 1155 mu mol.h(-1)-g(-1) with an apparent quantum yield of 6.8% at 420 nm monochromatic light, which is much higher than that of the optimized OD-2D Pt/g-C3N4 photocatalyst. The high photocatalytic H-2 production activity of 2D-2D MoS2/g-C3N4 photocatalyst can be attributed to the large surface area and the formed 2D interfaces between MoS2 and g-C3N4 nanosheets. As demonstrated by photoluminescence quenching and time-resolved fluorescence decay studies, the 2D interfaces can accelerate the photoinduced charge transfer, resulting in the high photocatalytic H-2 production performance. This study provides a new strategy in developing highly-efficient g-C3N4-based photocatalysts for H-2 production via using 2D nanojunction as a bridge to promote the photoinduced charge separation and transfer.