Abstract: To develop polyethylene terephthalate (PET) with long-acting antibacterial and antiviral properties, carboxymethyl chitosan quaternary ammonium salt (CMHTCC) was grafted onto the surface of 3-aminopropyltrimethoxysilane (APTMS) modified PET (APTMS/PET) by amidation reaction to prepare antibacterial and antiviral functionalized PET composites (CMHTCC-APTMS/PET). The effect of CMHTCC concentration on the antibacterial activity of CMHTCC-APTMS/PET was investigated to optimize the modification process of PET. The chemical structure and long-acting antibacterial and antiviral properties of CMHTCC-APTMS/PET were analyzed. The results show that the inhibition rates of CMHTCC-APTMS/PET against S. aureus and E. coli reached 99.99% at a CMHTCC concentration of 0.6w/v%. Furthermore, the modified PET shows superior antibacterial and antiviral efficiency. The inhibition rate of S. aureus and E. coli reached 99.99% (6 h), and the inhibition rate of bacteriophage MS2 reached 99.89% (1 h). Meanwhile, the covalent grafting of CMHTCC endows the modified PET with superior antibacterial and antiviral durability. The antibacterial and antiviral activity remains above 99% even after 30 washing cycles. In addition, the binary modification of PET by CMHTCC and APTMS improves its hydrophilicity (the contact angle decreases from 106.5° to 0°) and antistatic properties (the surface resistivity decreases from 2.24×10¹⁴ Ω/sq to 3.80×10⁷ Ω/sq), while maintaining excellent mechanical performance.