Recently, two-dimension g-C3N4 based materials have received tremendous attention, ascribing to its short charge diffusion distance and sufficiently exposed surface active sites. However, the poor charge separation and light harvesting still remains a great challenge for their practical applications. Herein, phosphorene/g-C3N4 heterojunction was constructed by simple introducing phosphorene which own visible light response and high mobility, to promote charge separation and light harvesting. Meanwhile, phosphorene can be regarded as effective co-catalyst for g-C3N4 to reduce the barrier of charge transfer between photocatalyst and electrolyte interface, and thus suppress charge recombination and improve photocatalytic hydrogen evolution rate. Compared to pure g-C3N4, the phosphorene/g-C3N4 heterojunction presents not only better charge separation and lower charge recombination, but also wider light response. As a result, the photocatalytic hydrogen evolution rate as high as 1.08 mmol?g-1?h-1 is achieved for phosphorene/g-C3N4 heterojunction, which is 1.2 times higher than the pure g-C3N4.