Abstract: The wood-based boards mostly bonded with urea-formaldehyde(UF) resin are the main reasons of formaldehyde pollution of indoor air.To master the curing mechanism of UF resin is the key for resolving the formaldehyde pollution problem.According to the traditional condensation polymerization theory,colloidal concept of UF resin,and some experimental and production facts,this paper discussed the formaldehyde content of UF resin,formaldehyde emission and water resistance of wood-based boards,and the effects of molar ratios and catalysts on the curing rate of UF resin,the existent problems of the traditional condensation polymerization theory,and the colloidal concept for explaining the curing mechanism of UF resin were clarified.