Abstract: The phenol-urea-formaldehyde(PUF) resins with 95%-200% urea (base in phenol weight) were synthesized in alkaline condition by using CaO and NaOH as catalyst. It had long storage life(>30 d). These PUF resins were used to produce the plywood that meet the requirement of type Ⅱ by measuring the bond strength. The formaldehyde emission of the PUF resin bonded poplar plywood was less than 0.5 mg/L, which was regarded as E0 degree. PUF resin was synthesized in the conduction of urea/phenol (U/P) mass ratio 1.5:1 and formaldehyde and urea-phenol (F/(U+P)) molar ratio 0.97. The contents of methylene, hydroxymethyl and methylene-ether bonds which transformed from formaldehyde molecule, were quantitatively examined by the 13C NMR spectroscopy. The relationships between the formaldehyde emission and the bond strength of the PUF resin bonded poplar plywood were explained by the analysis of the contents of methylene (32.4%), hydroxymethyl (57%) and methylene-ether (10 %) bonds.