Abstract: Magnesium-based hydrotalcite (MAL), aspartic acid (ASP)-loaded hydrotalcite (MALA), ASP and Ag⁺ co-loaded hydrotalcite (MALAA) were prepared by nucleation crystallisation, their hydrotalcite structure and morphology were characterised by X-ray diffraction and transmission electron microscopy． Both ASP and Ag⁺ were found successfully loaded onto MAL with morphological changes． Their antibacterial effect on Staphylococcus aureus (S. aureus) was examined by colony counting method． MAL inhibition of S. aureus growth was found to be 5.8% at 4 mg·mL⁻¹, but MALAA inhibition was 99.7%． The anti-bacterial mechanism of these modified magnesium-based hydrotalcites was examined by inductively coupled plasma and UV-visible spectrophotometer techniques． MALA was found adsorbed electrostatically on the negatively charged S. aureus, with changed MALA morphology, to increase the overall contact area with bacteria． Introduction of Ag⁺, by increasing the potential difference between MALAA and the bacterial cell surface, promoted the rupture of S. aureus cell membrane, leading to significantly-increased extracellular cations (K⁺, Ca²⁺, and Mg²⁺) and proteins． MALA but especially MALAA due to their antibacterial activities will be very useful packing materials in the food, cosmetics industries．