Background: Today, with the development of human life and the overwhelming fall of antibiotics and uncontrolled bacterial resistance, the need to find materials with antimicrobial effects is felt more than ever. Nanotechnology has created a new opportunity to investigate the antimicrobial effects of nanomaterials. Materials & Methods: In this study, using hydrothermal and microwave auxiliary chemicals, polylactic acid / calcium oxide nanostructures were prepared and the physicochemical and microbial properties of these nanostructures were evaluated. Bacterial strains were obtained from the Scientific and Industrial Research Organization of Iran, the collection center of industrial microorganisms. Results: Physicochemical characterization of optimized polylactic acid / calcium oxide nanostructures showed the antimicrobial effect of nanoparticles on 3 strains gram-positive bacteria Micrococcus luteus (PTCC 1110), Bacillus subtilis (PTCC 1023), Staphylococcus aureus (PTCC 1112) and 4 strains gram-negative bacteria Escherichia coli (PTCC 1330), Klebsiella pneumonia (PTCC 1053), Serratia marcescens (PTCC 1621), Pseudomonas aeruginosa (PTCC 1074). In this study, the observed MIC (minimum growth inhibition concentration) observed for both Gram-positive and Gram-negative bacteria ranged between 0.5