Abstract Various MnOx states played diverse roles in the selective catalytic reduction (SCR). Precursors and atmospheres had essential influence on valence conditions of MnOx. TiO2-supported manganese oxide catalysts were prepared from three different precursors in N2, O2 and air atmospheres. These samples were characterized by XRD, TG–DSC–MS and thermodynamic calculation. Characterization results showed that MnO2 was acquired by calcining manganese nitrate (MN) and TiO2 in air, while manganese carbonate (MC) and manganese acetate (MA) precursors both caused mainly Mn2O3 and Mn3O4. MA-MnOx/TiO2 catalysts calcined in nitrogen demonstrated active ingredients of MnO2, Mn2O3 and Mn3O4, but consisted of MnO2, Mn2O3, Mn3O4 and MnTiO3 calcined in oxygen. Different MnOx were identified by thermodynamic parameters and TG–DSC–MS studies.