With the global prevalence of infectious diseases, the development of antimicrobial textiles has become imperative. In this study, a synergistic antibacterial powder of IZnO–SCSB was obtained by modifying zinc oxide (ZnO) nanoparticles with 3-isocyanatopropyltriethoxysilane (IPTS) and chitosan cinnamaldehyde Schiff base (SCSB). The powder was then mixed with a PET solution and a PET/IZnO–SCSB composite antibacterial fiber membrane was prepared using electrospinning. This composite fiber membrane demonstrates excellent mechanical properties, breathability, hydrophobicity, and antibacterial effects. The tensile strength and elongation at break were 2.4 MPa and 240.9%, respectively. When the membrane was loaded with 3 wt% of IZnO–SCSB, the antimicrobial rates against Gram-positive ( S. aureus ) and Gram-negative ( E. coli ) reached 99.80% and 97.08%, respectively. Therefore, this composite antibacterial fiber membrane has broad application prospects in antibacterial textiles such as masks and medical gauze.