Unsupported catalyst was prepared by iron ore tailing selected from Nanshan mine of Ma?anshan iron & steel company limited. The catalysts were characterized by XRF, BET and XRD techniques. Experiments of catalytic reduction of NO over catalyst with NH3 were carried out in a quartz glass fixed-bed reactor. The results showed that the catalyst prepared by iron ore tailing presents a good catalytic activity for NO reduction at 500?600℃. The catalytic reduction rate can reach to 97.5% at 600℃. Moreover, the smaller the particle size, the higher the catalytic reduction rate. Increasing oxygen content can increase catalytic reduction rate of NO at 350℃. However, high oxygen content can decrease catalytic reduction rate of NO at 500℃. The higher the iron oxide content, the higher the catalytic reduction rate. But at high temperature, sintering of iron oxide can decrease the catalytic reduction rate.