The low denitration activity and stability of MnOx/TiO2 catalyst are still challenging. In this work, a MnOx/TiO2 catalyst was modified via a polarization effect with tourmaline. Tourmaline with a proper fineness can improve the denitration performance of the catalytic material, obtaining the greater denitration rate above 90% in a wide temperature range and the prolonged high-efficiency denitration time. Based on the results of in-situ Fourier transform infrared spectroscopy, the reaction mechanism of the catalysts before and after modification with tourmaline follows the Langmuir-Hinshelwood mechanism, and tourmaline polarization can accelerate the adsorption rate of reaction gas and generate intermediate products liable for subsequent reaction, thus improving the denitration performance.