Recently, air pollution is increasing sharply in Korea, caused by fine particulate matter. Nitrogen oxides (NOx) are particulate matter precursors that significantly contribute to air pollution. They are transmitted into the atmosphere by a large amount, especially in high-volume traffic areas. This pollutant is particularly harmful. Therefore, there are increasing efforts focused on NOx removal from the air. As the photocatalytic reaction of titanium dioxide (TiO2) is the mechanism that eliminates NOx, the ultraviolet (UV) rays in sunlight and TiO2 in existing concrete structure need to be contacted for reaction process. Generally, TiO2 concrete is produced by mixing the concrete binder with TiO2. However, a significant amount of TiO2 in the concrete cannot be exposed to air pollutants or UV. Additionally, this technique may not be applicable to existing structures. Therefore, an alternative method that utilizes surface penetration agents is used to add TiO2 to the concrete surface of the structures. This proposed method may not only be economical but also applicable to various types of structures. The applicability of the TiO2 penetration application method to existing concrete road structures for reducing NOx is the purpose of this study. The penetration depth of TiO2 particles was measured using scanning electron microscopy (SEM) combined with energy dispersive analysis of X-rays (EDAX). Additionally, the NOx removal efficiency was evaluated using the NOx analyzing system. The results of this study showed that the TiO2 penetration method was advantageous in removing NOx effectively and securing economic feasibility.