Formaldehyde inhibitor was prepared by the monolayer evaporation inhibition technology.The inhibitor could spontaneously spread on the formaldehyde surface to form an insoluble film.It controlled generation of formaldehyde gas by way of blocking its escape and changing the molecular structure of hydrated formaldehyde on the interface layer.The effect of temperature and filming concentration of the monolayer on transfer coefficient for formaldehyde on gas-liquid interface was discussed.Spreading performance of the inhibitor was determined using the surface pressure technique.The microstructure of the monolayer on the gas-liquid interface was described by Maxwell displacement current(MDC)and atomic force microscopy(AFM).The mechanism that the monolayer inhibited the generation and transport of formaldehyde was that the compactness of the monolayer reduced the transport of formaldehyde gas at the interface.Moreover，hydrated formaldehyde molecules could be formed，and the molecular interaction increased due to the existence of hydrogen bond.Thus formaldehyde became more stable and the formation of toxic gas was effectively inhibited.