Abstract: An antibacterial agent including a photocatalytic antibacterial material. The photocatalytic antibacterial material includes a rare-earth element modified tetrapod-shaped zinc oxide whisker (T-ZnOw). A method for preparation of the antibacterial agent is also provided, and includes: 1) adding a tetrapod-shaped zinc oxide whisker and a dispersant into a dispersion medium, and dispersing to yield a tetrapod-shaped zinc oxide whisker dispersion system; and 2) adding a rare-earth element to the dispersion system under ultrasound conditions, stirring, performing ultrasonic vibration, filtering, washing, drying, and baking, to yield the antibacterial agent.