The applications and production processes of solvent-based polyurethanes (PUs) are well developed. However, because of environmental and safety problems, solvent-based PUs are being gradually replaced by aqueous-based PUs, but their physical and mechanical properties are still insufficient in comparison with solvent-based PUs. The improvements in aqueous-based PUs in current technologies are normally achieved with post-curing reactions or polymer modifications, to enhance the molecular weight, crosslinking density and performance properties of PUs. In this article, the functionalities and modifications of aqueous-based PUs in recent years are introduced briefly.