catalytic oxidation of formaldehyde (HCHO) has been considered as one of the most promising approaches because this process is environmentally friendly, energy-saving, simple operation and so on. In this paper, the active oxygen species, the possible intermediates and the reaction paths in the catalytic oxidation of HCHO have been summarized. And the main factors that influence the reaction mechanisms of catalytic HCHO oxidation over the noble metal catalysts (such as Au, Pt, Pd and Ag) and transition metal oxides (such as Mn, Co and Ce) have been reviewed in terms of the different metal species, carrier properties and additives. The reaction mechanism of commercial formaldehyde removal products was introduced. At last, the existing problems in the mechanism of catalytic oxidation of formaldehyde and the opportunities for future research were prospected.