Ti-doped graphitic carbon nitrides (g-C3N4) were obtained through calcining the mixture of melamine and tetrabutyl titanate. The structure and Ti atom position of Ti-doped g-C3N4 were identified through X-ray diffraction (XRD) patterns, X-ray photoelectron spectra (XPS) and first principle calculations. After doping, the degradation rate of Rhodamine B (RhB) was improved almost 4 times under visible light irradiation, which was further confirmed through theoretical and experimental analysis. According to photoluminescence (PL) spectra, photocurrent and ultraviolet-visible (UV-vis) absorption spectrum, enhanced separation rate of photogenerated carriers and modified electronic structure were estimated. These results supplement the current understanding on photocatalytic processes of doping system and the mechanism of layered photocatalysts.