Mesoporous MnO₂ was prepared by sol-gel method using KMnO₄ and P123. The structure and properties of the synthesized materials were characterized by XRD, N₂ adsorption and desorption, and FT-IR. The effects of reactant ratio and pH on the catalytic oxidation performance of the product were investigated. The optimum conditions of the preparation were as follows: the ratio of KMnO₄ and P123 was 10:1 and the pH was 7. The results shown that mesoporous MnO₂ has good catalytic oxidation performance to HCHO. Finally, the influencing factors of the catalytic oxidation of HCHO by mesoporous MnO₂ were discussed. The specific surface area of mesoporous MnO₂ (pH7-10:1) was largest. The oxidation performance was the strongest, and the degradation rate of formaldehyde was maintained at 95 %.