Abstract: With the development of industrial production and road transportation, the emission of nitrogen monoxide (NO) is becoming increasingly severe. To degrade NO effectively, Fe-doped g-C₃N₄/TiO₂ heterojunction composite photocatalysts (Ti-FeCN) were fabricated using a two-step thermal polymerization method, employing melamine, ferric nitrate nonahydrate, and titanium dioxide as raw materials. The photocatalytic performance was evaluated based on the degradation of NO, and the degradation mechanism was further investigated through free radical trapping experiments. The results indicated that the sample Ti-FeCN-4 exhibited the highest NO degradation rate of 37.7% under visible light conditions, which is 2.4 times greater than that of pure TiO₂. Notably, the degradation rate decreased by only 3.1% after five cycles. The enhanced photocatalytic activity is attributed to the Z-type heterojunction formed by FeCN and TiO₂, which significantly broadened the visible light absorption range, increased the number of active sites, and reduced the recombination of photogenerated electron-hole pairs.