Ochratoxin A (OTA) is the predominant mycotoxin in fermented meat products and poses a serious threat to consumer health. Highly effective and safe plant essential oils and their active components represent ideal natural antifungal agents. This study developed cinnamaldehyde nanoemulsion (Cin-Ne) as an antifungal agent to target the risk of OTA exposure caused by mold contamination in fermented meat products. The average particle size, polydispersity index (PDI), and Zeta potential of Cin-Ne were measured over 28 days of storage at 4 ℃ using dynamic light scattering (DLS). Results demonstrated that Cin-Ne exhibited good storage stability: The average particle size increased from 168.3 nm to 218.8 nm, the PDI remained stably below 0.18, and the Zeta potential consistently exceeded 28 mV. In vitro antifungal assays revealed that the half-maximal effective concentration (EC₅₀) of Cin-Ne against Aspergillus niger A-8 was 0.073 mg/g. Cin-Ne significantly inhibited key developmental stages of A. niger A-8, including mycelial growth, spore germination, and sporulation (P<0.05). In a fermented sausage model, the surface application of Cin-Ne (2×EC₅₀) onto casings significantly suppressed A. niger A-8 growth and reduced OTA levels. By the end of fermentation, OTA content in the casings and stuffing was significantly reduced by 58.4% and 52.1%, respectively (P<0.05). Cin-Ne combated A. niger A-8 through multiple pathways: Disrupting cell membrane integrity (increased relative electrical conductivity, decreased ergosterol content), interfering with energy metabolism (reduced activity of key tricarboxylic acid (TCA) cycle enzymes and ATPase, decreased ATP levels), inducing oxidative stress (dysregulation of antioxidant enzyme activity, excessive accumulation of reactive oxygen species accompanied by lipid peroxidation), and activating the mitochondrial apoptosis pathway (mitochondrial membrane potential depolarization, cytochrome c release into the cytosol). The developed Cin-Ne demonstrates potential as a natural antifungal agent, offering a novel strategy for preventing OTA contamination in fermented meat products.