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Selective catalytic reduction (SCR) of NO x with NH 3 has been widely used for the removal of NO x. Because of the inevitable disadvantages of conventional V 2 O 5 -WO 3 (MoO 3)/TiO 2 catalysts such as poor low-temperature SCR activity and toxicity of vanadium, as well as the high-cost and over-strong NH 3 adsorption of zeolite catalysts, the development of efficient and non-toxic metal oxide SCR catalysts is highly demanded. Previously, we have developed an environmentally-benign CeO 2 -SiO 2 mixed-oxide SCR catalyst (CeSi 2), which exhibited superior SO 2 resistance ability. However, the low-temperature SCR activity on CeSi 2 was not that satisfactory. In this work, we proposed a new strategy of Mo doping to improve the low-temperature SCR activity on CeSi 2 , which was very crucial for its practical application. By a simple co-precipitation method, a homogenous Mo-Ce-Si mixed-oxide catalyst was prepared. The Mo doping could significantly enhance the NH 3 -SCR activity on CeSi 2 below 250 °C, and the optimal catalyst was Mo 0.1 CeSi 2 , which could achieve 80% NO x conversion at 200 °C. Mo 0.1 CeSi 2 also exhibited superior N 2 selectivity and resistance to SO 2 /H 2 O poisoning. Via a series of characterizations, it was found that the redox properties and surface acidity on CeSi 2 by Mo doping, which accounted for the enhanced low-temperature NH 3 -SCR activity on Mo 0.1 CeSi 2. The reaction mechanism on Mo 0.1 CeSi 2 was also fully revealed by in situ DRIFTS experiments. This work provided a new insight for the development of efficient low-temperature SCR catalysts with superior SO 2 resistance ability. [Display omitted] • A homogeneous Mo-Ce-Si mixed-oxide catalyst was prepared. • Enhanced low-temperature NH 3 -SCR activity was achieved on Mo doped CeO 2 -SiO 2. • Mo-Ce-Si catalyst exhibited excellent resistance to SO 2 poisoning. • Surface acidity and redox properties of CeO 2 -SiO 2 were promoted by Mo doping. • NH 3 -SCR reaction on Mo-Ce-Si catalyst proceeds through E-R mechanism. [ABSTRACT FROM AUTHOR]