Exploring an efficient and inexpensive noble-metal-free co-catalyst to replace noble-metal is a huge challenge for photocatalytic H-2 evolution. Transition metal phosphides (TMPs) as co-catalysts for photocatalytic H-2 generation have been extensively employed due to their exceedingly good property, stability and low cost. Herein, a new photocatalyst containing g-C3N4 and porous network-like MoP as a highly efficient co-catalyst was fabricated. The maximal H-2-generation rate of the MoP/g-C3N4 photocatalyst could reach 327.5 mu mol.g(-1) h(-1), which was similar to 3.4 times higher than that of pure g-C3N4. The quantum efficiency achieved 9.6% at 400 nm. The improvement in photocatalytic H-2-generation of MoP/g-C3N4 was resulted from the proper Fermi level alignment and the close contact interfaces of porous network-like MoP and g-C3N4, in which MoP not only increased light absorption but also fasted the separation and transfer of photogenerated carriers as well as lowered the H-2 evolution overpotentials. The possible photocatalytical mechanism of the MoP/g-C3N4 photocatalyst was speculated based on various characterization techniques. It is believed that this study can offer a novel pathway to design highperformance and low-cost photocatalytic materials composed of metal phosphide co-catalyst for efficient watersplitting H2-generation over semiconductors under visible-light illumination.