A simple and repeatable method has been developed to synthesize g-C3N4 via a pyrolysis of protonated precursors, with the simultaneous doping and controlled morphology. Protonated precursors with morphology of polyhedrons, nanoflakes, and nanowires are achieved after melamine has been treated by sulfuric acid, phosphoric acid, and nitric acid, respectively. After pyrolysis of protonated precursors, as-attained S-g-C3N4 (derived from sulfuric acid treated melamine) exhibit remarkable photocatalyst performance owing to a delicate band gap and high specific surface area. Specifically speaking, an H-2 evolution rate of S-g-C3N4 (0.473 mmol/h) is about four times than that of N-g-C3N4 (derived from nitric acid treated melamine). Besides, S-g-C3N4 can endow a complete degradation of RhB within 120 min. The merits of this research provide a universality and reproducible approach to synthesize novel photocatalyst for energy conservation and environmental protection.