Abstract: The authors selected several suitable modifiers to enhance the hydrophobic strength of soy adhesive at different phases. The technology of the pressing-board with composite modified soy adhesives is established and tested. The test results show that soy power and polyphenylene polyisocyanate（PAPI）are two more important factors affecting the hdrophobic strength of the soy adhesive. The best modification prescription is 21% soy powder, 1.0% sodium dodecyl sulfate(SDS), 1.5 mol·L-1 urea, 1.2% anhydride and 20% PAPI. The pressing-board technology shows that hot-press temperature is the most significant factor in determining the hydrophobic strength of adhesives. It is most efficient at a hotpress temperature of 140 ℃, specific pressure of 1.2 MPa and hot-press duration of 1.0 min·mm-1. The average hydrophobic strength of the modified soy adhesives is 0.94 MPa. It can serve as urea resin because it meets grade II glue and free formaldehyde waterproof requirement. Furthermore, the modified adhesives are harmless and environmentally friendly, with high marketability as well as socio-ecological benefits. Fourier transform infrared spectroscopy (FTIR) validates the principles of waterproof development and chemical mechanism of the compositely modified soy-based wood adhseive.