V2O5/TiO2 catalysts promoted with Mn were prepared and tested for selective catalytic reduction of NOx in NH3. The effects of promoter content, degree of catalyst loading were investigated for NOx activity while changing temperatures, mole ratio, space velocity and O2 concentration. Among the various V2O5 catalysts having different metal loadings, V2O5(1 wt.%) catalyst showed the highest activity(98%) under wide temperature range of 200-250℃. When the V2O5 catalyst was further modified with 5 wt.% Mn as a promoter, the highest activity(90-47%) was obtained over the low temperature windows of 100-200℃. From Mn-V2O5/TiO2, it was found that by addition of 5 wt.% Mn on V2O5/TiO2 catalyst, reduction activity of catalyst was improved, which resulted in the increase of catalytic activity and NOx reduction. According to the results, NOx removal decreased for 10%, but the reaction temperature down to 100℃.