Abstract: The effects of final molar ratio of UF resin modified by melamine on capability(solid content,gelation time,free formaldehyde content)of modified resin and plywood performance(glue bond strength,prepressing intension,formaldehyde emission)were studied.The variables included the final ratio of UF,the quantitative change of melamine,polyvinyl alcohol and the temperature of final.The experiment was designed by the mathematical model of "Quadratic orthogonal rotation combination design".According to the results of the experiment,while the final molar ratio of UF increased,the solid content followed decreased.The gelation time notably shortened while the final molar ratio of UF increased.Not only the final ratio of UF,but also the craftwork and the temperature influenced the free formaldehyde content.Glue bond strength increased too while the final ratio of UF increased.While the final molar ratio of UF increased between 1.0 and 1.1,the prepressing intension followed decreased;while the final molar ratio of UF increased between 1.1 and 1.40,the prepressing intension followed also increased.There does exist linear relationship between formaldehyde emission and the final ratio of UF.