Low-temperature oxidative degradation of formaldehyde (HCHO) using non-noble metal catalysts is challenging. Herein, novel manganese dioxide (MnO2)/N-doped carbon nanotubes (NCNT) composites were prepared with varying MnO2 content. The surface properties and morphologies were analyzed using X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and transmission electron microscope (TEM). Comparing with MnO2/carbon nanotubes (CNTs) catalyst, the 40% MnO2/NCNT exhibited much better activity and selectivity for HCHO oxidation, mineralizing 95% of HCHO (at 100 ppm) into CO2 at 30 °C at a gas hourly space velocity (GHSV) of 30,000 mL h-1  g-1. Density functional theory (DFT) calculation was used to analyze the difference in the catalytic activity of MnO2 with CNTs and NCNT carrier. It was confirmed that the oxygen on NCNT was more active than CNTs, which facilitated the regeneration of MnO2. This resulted in remarkably boosted activity for HCHO oxidation. The present work thus exploited an inexpensive approach to enhance the catalytic activity of transition metal oxides via depositing them on a suitable support.