Bacterial infections have one of the extensive impacts on public health. Therefore, finding compounds with antibacterial properties could serve as an effective method. In this work, a nanocomposite, Ag/CaO was prepared from silver nitrate and egg shells. After calcination of the egg shells at 900°C, the solid remaining, CaO was cooled, then silver nitrate was added and the mixture was ground to a fine powder, and finally heated at 300°C. The brown solid obtained was characterized by SEM, XRD and XRF methods. Afterwards, the prepared Ag/CaO nanocomposite was applied and compared with CaO for antibacterial activity against gram positive and gram negative bacteria. The used bacteria were pseudomonas aeruginosa, keleb pneumonia, staphylococcus aureus, staph saprophyticus, Ecoli.