Abstract: Glyoxal (G) partially substituted for formaldehyde (F) and urea (U) to prepare GUF co-condensed resin. The effects of synthesis conditions on the basic properties of the GUF resins were studied. Dynamic thermo-mechanical analysis(DMA)was used to simulate the hot press process of the GUF-bonded plywood panels and investigate the curing property of the GUF resins. Then the mechanical properties and formaldehyde emission of the plywood panels bonded with the GUF resins prepared under the optimized condition were studied. And these results indicated that the optimum synthesis condition of GUF resin was that glyoxal and urea react was 70-80 ℃ for 1 hour when its pH value was 4.0-5.0, then adding formaldehyde and react for 2 h when its pH value was 5.0-6.0 and n_G:n_U:n_F is 0.7:1.0:0.7. Under the optimized conditions, the dry internal bond strength and formaldehyde emission of the GUF-bonded plywood panels could meet the relative requirement of China national standard GB/T 9846.3-2004, and the panels could be directly used indoor under dry conditions.