Abstract: Alicyclobacillus acidoterrestris is an acidophilic and thermotolerant bacterium, which can grow in acidic beverages such as apple juice, causing off-flavors and even sedimentation, ultimately leading to spoilage. To control the contamination of A. acidoterrestris in apple juice, this study focused on the natural antibacterial agent curcumin. Through experiments including the determination of the minimum inhibitory concentration (MIC), conductivity analysis, evaluation of cell membrane damage, intracellular ATP content, and intracellular pH, the inhibitory activity and potential mode of action of curcumin against A. acidoterrestris were investigated. Additionally, the effects of curcumin addition on the physicochemical properties of apple juice at 4 ℃ (cold chain transportation temperature) and 25 ℃ (room temperature) were explored. The results showed that the MIC of curcumin against this bacterium was 0.1 mg/mL, and its antibacterial effect was mainly achieved by disrupting the integrity of the bacterial cell membrane, reducing intracellular ATP content and pH. The addition of curcumin to apple juice, combined with low-temperature storage, effectively inhibited A. acidoterrestris while maintaining key physicochemical parameters, such as pH (3.29±0.01), sugar content (13.33±0.06 °Brix), total phenolic content (202.22±1.80 μg/mL), and color difference (ΔE≤0.63), within normal ranges. These findings demonstrate that curcumin can effectively prevent A. acidoterrestris contamination in apple juice, providing a theoretical basis for the control of thermophilic acidophilic bacteria in acidic beverages.