Abstract: Catalytic activity and SO₂ resistance of a series of Mn-based perofskite type catalysts, La_1-xSr_xMn_1-yMe_yO₃, (x=0, 0.1, 0.2, 0.3, 0.4; y=0, 0.2, 0.4, 0.6), have been investigated. Their reducibility has been studied by means of TPR method. Adsorption of SO₂ on catalysts' surface has been studied by means of FTIP. Those results showed: Mn-based perofskite type catalysts catalyzied CO to CO₂ following adsorption mechanism. The more the low valence Mn ions were, the stronger theability of catalysts' adsorbing oxygen was, the lower the TPR temperature was, the higher the reducibility of catalysts was and the better the activity of catalysts was as well. SO₂ strongly adsorbed on Mn ions of B site incapacitated catalysts from adsorbing oxygen and made catalysts irreversibly inactive.