The development of low-temperature SCR catalysts is of vital importance due to their potential application in downstream of the desulfurizer and electrostatic precipitator, where the flue gas temperature is usually bellow 473 K. In this study, various Mn-based nanobelts were synthesized by a facile redox-precipitation route and were further used as low-temperature SCR catalysts. In particular, the as-prepared alpha-MnO2 nanobelts with exposed (1 1 0) surface were shown to be single crystallites with widths of 10-20 nm and lengths of 50-200 nm. The alpha-MnO2 with porous and hierarchical nanostructure interweaved by alpha-MnO2 nanobelts presented large specific surface area and exhibited high NO conversions and wide operating temperature window, reaching up to above 90% NO conversion within the testing range of 393-453 K. An Eley-Rideal (E-R) reaction mechanism is proposed with Bronsted acid sites involved in the SCR reaction for alpha-MnO2. The possible growth mechanism of alpha-MnO2 nanobelts was also tentatively discussed.