Physicochemical properties of four different sodium lignosulfonates were studied through FTIR, elemental analysis and GPC. Meanwhile, these lignosulfonates were used to synergistically modify soybean adhesives with polyamideamine-epichlorohydrin. Then, the wettability and rheological properties of the adhesive, as well as the wet bonding strength of the resulting plywood were investigated. As displayed in FTIR spectra of different sodium lignosulfonate, a peak corresponding to S=O of sulfonic group appeared at 1065 cm-1. With higher content of sulfonic groups in the sodium lignosulfonate, zero shear viscosity of the modified soybean adhesive was lower and its wettability on the surface of wood was better, of which the contact angle decreased from 95 ° to 61 °. The wet bonding strength of plywood made using soybean adhesive modified with liquid sodium lignosulfonates and polyamideamine-epichlorohydrin reached 0.92 MPa with 100% percent of pass, which met the national standard for type II plywood (≥0.70 MPa，≥90%).