Abstract: The sol-gel method was used to green synthesize ZnO nanoparticles (Nano-ZnO) with Spartina alterniflora(SAF) leaf extract, and the surface morphology, active groups, crystal structure and light absorption characteristics were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS), and the photocatalytic degradation activity of Nano-ZnO on Malachite green (MG) and the antibacterial properties of Staphylococcus aureus were analyzed. The results show that the green synthesis of Nano-ZnO with SAF extract has abundant oxygen-containing active groups, smaller particle size and good dispersibility. The calculated band gap energy of Nano-ZnO is 3.09 eV, which indicates that its efficiency of light absorption and utilization has been improved. The degradation efficiency of Nano-ZnO on malachite green reaches 98.2% in visible light, h⁺ and ·O^2- are the main active species that play a role in the photocatalytic degradation process. The antibacterial rate of Nano-ZnO against Staphylococcus aureus is twice that of ZnO. This study provides a new way for the high-value utilization of SAF and a new method for the preparation of nano-metal oxides.