Biocidal functionalization in polyester fibers is a really tough challenge because of the lack of tethering groups. This study indicated supercritical carbon dioxide application using N -halamine would be an alternative solution for obtaining antibacterial function on the polyester surface. Firstly, N -(2-methyl-1-(4-methyl-2,5-dioxo-imidazolidin-4 yl)propan-2 yl)acrylamide was synthesized and applied to the polyester in supercritical carbon dioxide medium, at 120 °C, 30 MPa for different processing times. The addition of N -halamine on the surface significantly brought antibacterial activity against E. coli . The chlorine loadings showed that 6 -h exposure time was critical to obtain sufficient antibacterial activity. This treatment caused a reasonable and tolerable loss in color and mechanical properties. But, the durability to abrasion, stability, and rechargeability of oxidative chlorine, and the durability of N -halamine on the surface were remarkably good. Conclusively, it can be available to work on polyester surfaces with resource-efficient and eco-friendly supercritical carbon dioxide technique for getting more functionalization and modification.