In this study, LaMn1-xFexO3 (x = 0, 0.3, 0.5, 0.7, 1) and La(0.8)A(0.2)Fe(0.7)Mn(0.3)O(3) (A = Sr, Cs, Ba, Ce) perovskite oxides were synthesized by sol-gel method and their activities were evaluated in catalytic reduction of NO by CO. Perovskite catalysts were characterized by XRD, BET, H-2-TPR, XPS and SEM. Synthesized perovskites present a high activity for the catalytic reduction of NO by CO, LaMn0.3Fe0.7O3 Show the highest activity among LaMn1-xFexO3 perovskite catalysts (71 % CO conversion and 82 % NO conversion at 350 A degrees C). The effect of partial substitution of Sr, Cs, Ba and Ce in A-site was also examined on the structure and catalytic activity of LaMn0.3Fe0.7O3 perovskite catalyst. La0.8Sr0.2Fe0.7Mn0.3O3 and La0.8Ce0.2Fe0.7Mn0.3O3 present the highest activities among La(0.8)A(0.2)Fe(0.7)Mn(0.3)O(3) perovskites. The introduction of Sr2+ and Ce4+ in A-site of perovskite change the reducibility of B-site cations and Fe4+/Fe3+ and Mn4+/Mn3+ ratios, and increase O-ads/O-latt ratio and these factors create structural defects in perovskite which lead to higher catalytic activities.