This work aims to study the toughening effect of waterborne polyurethane (WPU) on polyvinyl alcohol (PVA). The PVA/WPU blend membrane was prepared by adding WPU with a solid content (mass fraction) of 35% into the PVA aqueous solution with a solid content of 5% and mixing, defoaming, pouring and drying. FTIR, SEM, DSC and DMA were used to characterize the blend membrane, and the mechanical properties, water contact angle and water absorption of the blend membrane were tested. The result showed that with the increase of WPU content, compared with pure PVA, the stretching vibration peak of hydroxyl (—OH) of the blend membrane moved to the direction of high wave number; the crystallinity decreased; the tg decreased; the tensile strength decreased; the elongation at break increased; the water contact angle increased; the water absorption decreased; and the visible light transmittance decreased. It is concluded that the addition of WPU can improve the toughness of PVA/WPU blend membrane. When the mass fraction of WPU is 20%-30%, the blend membrane with better comprehensive properties can be obtained.