Graphitic carbon nitride (g-C3N4) is a fascinating metal-free photocatalyst for active solar hydrogen production. However, the photocatalytic activity of pristine g-C3N4 is dramatically restricted by the inherent shortcomings of fast charge recombination because of incomplete polymerization. Thus, increasing the extent of polymerization can be one of an efficient way to enhance its photocatalytic activity. Herein, a molten salt post-treatment approach has been developed to reconstruct pristine g-C3N4, in which molten salts serve as a generalist for accelerating the polycondensation and deamination reaction. This approach endows g-C3Nx with enriched nitrogen defects, and unique electronic structure, which results in narrower bandgap and higher electrical conductivity, significantly improve visible light harvesting capability and separation efficiency of charge carriers. As a consequence, the g-C3Nx shows 2.2 times higher the H-2 evolution rate than bulk g-C3N4. This discovery may open a novel avenue to fabricate highly efficient g-C3N4 catalysts.