In this paper, a series of new environmentally friendly bioadhesives with improved bonding strength were quickly synthesized via urea, sodium dodecyl sulfate (SDS) and propanetriol are mixed with soy isolate protein. The results showed that the bonding strength of the modified adhesives was changed with the increasing content of propanetriol. The maximum dry shear strength of the plywood bonded with the resultant adhesive was increased to 2.45MPa when the propanetriol content was 20ml. While the maximum wet shear strength of the plywood bonded with the resultant adhesive arrived 1.32MPa, which is acceptable for industrial application in plywood fabrication according to the national standards of the People's Republic of China (0.7MPa). In addition, the orthogonal experiment suggested that the obtained material with pH of 9 for 5h mixing at the hot pressing temperature of 120 degrees C exhibited the best comprehensive performance. Also, the FTIR, SEM and DSC measurements showed that the adhesives had a compact structure with stable thermal property.