To enhance the physicochemical properties of micro-nano bubbles (MNBs), the effects of salt ions on the physicochemical characteristics and bactericidal performance of MNBs prepared using high-speed vortex ultrasound technology were investigated. MNBs were prepared using different salt ions (magnesium sulfate, calcium chloride, and sodium bicarbonate) combined with high-speed vortex ultrasound technology. The bubble size, dissolved oxygen content, oxidation capacity, and bactericidal effects against Escherichia coli and Staphylococcus aureus were the key parameters systematically evaluated. The results showed that at a low concentration (0.01 mol•L-1), magnesium sulfate, calcium chloride, and sodium bicarbonate reduced the bubble size from 1 854.7 nm to 428.0, 474.8, and 516.2 nm, respectively, and increased the dissolved oxygen content by 14.09%, 34.04%, and 14.32% and the oxidation capacity by 48.33%, 48.08%, and 42.59%, respectively. Compared with that of the control, the bactericidal rate of salt ion-containing MNB water nearly doubled against both bacteria. This enhancement may be due to the fact that low concentrations of salt ions can promote the diffusion and reactivity of bubbles by enhancing their ionic hydration and electric double layer repulsion, thereby improving the physicochemical properties and bactericidal performance of MNB water. This study provides a theoretical basis and technical support for enhancing the cleaning efficacy of MNBs prepared using ultrasound-assisted synergistic methods.