This research aims to improve viscosity of waterborne polyurethane adhesive by the optimal preparation technology. Response surface analysis was applied to gain the optimal preparation technology of waterborne polyurethane adhesive. Effect on viscosity of waterborne polyurethane adhesive of the prepolymer, modifier, flexibilizer concentration and the interactions were studied to gain the optimal preparation technology. The results showed that the theoretical predictions (2716.64 mPa•s) agreed well with the experimental results (2658.32 mPa•s) when there were 47.24% (mass percent) prepolymer, 6.24% (mass percent) modifier, 5.84% (mass percent) flexibilizer, and 40.68% (mass percent) solvent. Response surface analysis can be used for optimization preparation technology of waterborne polyurethane adhesive.