Abstract: A new biomass thermosetting starch-furfural adhesive has been synthesized with furfural and starch under acidic or alkaline conditions. The physical and chemical properties of these adhesives and the dry and wet shear strengths of the plywood had been tested. The curing behavior was studied by differential scanning calorimetry(DSC), and its structure was determined by electrospray ionization mass spectrometry(ESI-MS). The results showed that the con-polymerization has been establishment between starch and furfuryl alcohol, which was mainly jointed by the bond of －CH₂－O－ under a pH of 5 and the mass ratio of furfural to starch of 1∶2. The addition of furfural reduced the gel time of starch adhesive. The dry and wet shear strengths of plywood prepared with starch-furfural adhesive synthesized under weak acidic condition was better than that of plywood based on starch-furfural adhesive prepared under alkaline condition.