The invention discloses a tough aldehyde-free soybean meal-based wood adhesive and a preparation method thereof. The adhesive comprises, by weight, 30-33 parts of a main agent, 70 parts of dispersed medium water, 3-6 parts of a reinforcing agent, 0.1-0.2 part of a viscosity regulator, 2-4 parts of a crosslinking agent and 0.3-0.6 part of a catalyst. The preparation method comprises the following steps of weighing each component according to the corresponding weight ratio first, adding the crosslinking agent into the dispersed medium water, adding the main agent and the reinforcing agent, and homogenizing and emulsifying the mixture for 20 minutes under the action of an emulsifying force of 0.5 MPa at the pressure of 30 MPa through a high-pressure homogenizer; then, adding the catalyst into the obtained mixture, triggering a reaction at 80 DEG C for 30 minutes, cooling a finished product to 30 DEG C, and then discharging the finished product. The adhesive is likely to form a crosslinking structure, high in crosslinking density and low in reaction temperature; the prepared adhesive is stable in performance, the weak interface layer is obviously reduced, the cost is lowered, the dry/wet strength is high, and the product quality is stably improved.