Abstract: Suspended pathogens in the air pose a significant threat to human health, emphasizing the need for effective antibacterial air filters. This study utilizes chitosan (CS) and tannic acid (TA) as raw materials to develop a CS-TA nanogel air filter via freeze-drying technology, which modifies the morphology of an F5 medium-efficiency filtration membrane. The microstructure, antibacterial properties, and filtration performance against suspended bacteria were investigated. The CS-TA membrane features an irregular porous structure with an average pore size of 3.39 nm. It exhibits more than 95% antibacterial efficacy against T4 bacteriophage, Serratia marcescens, and Escherichia coli. In environments ranging from 20°C to 30°C and 25% RH to 75% RH, its filtration efficiency for T4 bacteriophage increases by 47.99%, compared to the control membrane, while for Klebsiella pneumoniae, it improves by 40.83%. The CS-TA membrane demonstrates excellent antibacterial effects and retention capabilities against bacteria and viruses. This method is environmentally friendly, cost-effective, and simple, making it a promising solution for indoor air purification.