Graphitic carbon nitride (g-C 3 N 4 ) has been extensively applied for NO removal due to its striking visible-light response and outstanding stability. However, the toxic NO 2 product is not completely suppressed in the reaction process due to its poor photo-oxidation ability. Herein, a series of SnO 2 /g-C 3 N 4 composites were successfully prepared by the decorated of SnO 2 quantum dots (QDs) onto g-C 3 N 4 sheets. The experimental results demonstrated that SnO 2 /g-C 3 N 4 exhibited excellent visible-light response and enhanced photo-oxidization ability to inhibit the generation of NO 2 . Moreover, the heterostructure between SnO 2 and g-C 3 N 4 promotes the separation of photogenerated electron-hole pairs, which is resulted in enhanced photocatalytic NO removal performance. More importantly, the in-situ diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) measurement and electron spin resonance (ESR) are conducted to investigate the reaction pathway via detecting the generated intermediates, products and active radicals during NO removal process. This study provides a facile and effective method to enhance the efficiency of photocatalytic NO removal and suppress the concentration of NO 2 significantly.