To clarify the effect of N sources on the photocatalytic reduction of Re (VII) in amorphous TiO₂/g-C₃N₄ (TCN) composites, g-C₃N₄ were prepared via a thermal decomposition of three precursors (Urea, Thiourea and Melamine). Three kinds of TCN composite photocatalysts were then prepared by recombining with amorphous TiO₂ separately. All three photocatalysts were characterized by differnent methods, and their differences in photocatalytic reduction of Re(VII) were compared in detail. The experimental results show that U-TCN using urea as the N source has more uniform appearance, the largest specific surface area (474 m²/g), and the most excellent light absorption performance, leading to its photocatalytic reduction efficiency (90%) for Re (VII) being significantly higher than T-TCN (20%) and M-TCN (15%). Transient photocurrent and electrochemical impedance (EIS) analyses prove that U-TCN exhibits the highest efficiency of photo-generated electron/holes separation. Electron paramagnetic resonance spectroscopy (EPR) analysis shows that U-TCN generates more hydroxyl radicals (·OH), so that there are stronger reducing ·CO₂ radicals produced by the reaction with formic acid, which is more conducive to the reduction of Re (VII). X-ray absorption spectra are employed to analyze the valence state and coordination environment of Ti element, which demonstrates an excellent photochemical stability of U-TCN. The study not only illustrates the effects of N sources on the photocatalytic performance of TCN composites, but also provides a promising photocatalyst for reduction and removal of Tc(VII) from waste water.