Graphitic carbon nitride (g-C3N4) was synthesized by one-step calcination at different temperatures for enhanced photodegradation of 2-naphthol under visible light (lambda >= 420 nm). The g-C3N4 photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR) and ultraviolet-visible diffuse reflectance spectra (UV-vis DRS). The morphology, band structure and optical property of g-C3N4 could be controlled by the calcination temperature. The formation of genuine g-C3N4 actually began when the temperature was higher than 500 degrees C. Moreover, compared to the primary stage (450 degrees C) and the intermediate stage (500 degrees C and 550 degrees C), the g-C3N4 synthesized at the advanced stage (600 degrees C and 650 degrees C) had not only the strongest absorption of visible light but also the narrowest band gap, enabling controllable adjustment of the band structure of catalysts. Furthermore, the photodegradation efficiency of 2-naphthol was improved as the calcination temperature of g-C3N4 rising up. Meanwhile, g-C3N4 synthesized at 600 degrees C performed the best with a rate constant of 1.949 h(-1) for the first-order kinetic model, which was 2.67 times that of the catalyst synthesized at 450 degrees C. Finally, the possible photodegradation pathway of 2-naphthol by g-C3N4 was proposed.