The influence of cerium (Ce) on the structure and properties of automotive catalyst LaMO 3 (M=Mn or Mn-Cu) and washcoat materials γ-Al 2 O 3 has been analyzed by a combination of scanning electron microscopy (SEM), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), and catalytic test studies. The results showed that the thermostability of the washcoat was positively improved by adding Ce into γ-Al 2 O 3 . The temperature of phase transformation from γ- to α-Al 2 O 3 was modified from 800 to 1150 o C with 6% ceria. At the same time, the washcoat of γ-Al 2 O 3 still presented the maximum surface area. On the other hand, by adding Ce into the perovskite-type catalyst LaMn 0 . 7 Cu 0 . 3 O 3 + λ , the oxidation ability of active materials had a little decrease due to the conversion of hydrocarbon (HC). However, the oxidation ability of carbon monoxide (CO) and the reduction ability of nitrogen monoxide (NO) using the catalyst LaMn 0 . 7 Cu 0 . 3 O 3 , were greatly modified. In the oxygen-rich gas with 10% O 2 , the conversion rate of NO x was greatly increased to over 40%, using the catalyst LaMnO 3 /Au doped with Ce. Not only were the formation and separation of perovskite crystals restrained by Ce additive, but the crystal size also decreased, so as to make a better distribution of active component on the surface.