Removal of NOx on CaO/TiO2 photocatalyst manufactured by the addition of Ca(OH)2 was measured in relation with the amount of Ca(OH)2 and calcination temperature. In case of pure TiO2, the NOx removal decreased greatly with the increase of calcination temperature from 500oC to 700oC, whereas in the photocatalyst added with Ca(OH)2, the removed amount of NOx was high and constant regardless of calcination temperature. Considering NOx removal patterns depending on the amount of Ca(OH)2 added(50, 30, 10wt%), high removal rate showed at the photocatalysts containing less than 30wt% of Ca(OH)2, and it was about 30% higher than that of pure TiO2. From the XRD patterns, it is seen that the addition of Ca(OH)2 contributes to maintaining the anatase structure that is favourable to photocatalysis. It also indicates that the possibility of the formation of calcium titanate(CaTiO3) by reacting with TiO2 above 700oC. Apart from the favourable crystalline structure, the addition of Ca(OH)2 helped increase the alkalinity of photocatalyst surface, thus promoting the photooxidation reaction of NOx.