Abstract: 【Objective】This study aimed to clarify the species and biological characteristics of pathogens causing postharvest Annona atemoya soft rot， and to investigate the inhibitory effects of aldehyde-based antimicrobial agents on Annona atemoya soft rot pathogen， thereby providing a theoretical reference for controlling this disease.【Method】Fruits of Juran Bash No.1 Annona atemoya collected from the demonstration planting base in Bapen Town， Fusui County， Chongzuo City， Guangxi， were used as experimental materials. Pathogens were isolated and purified from diseased fruits showing soft rot symptoms after natural postharvest storage using the tissue separation method. Pathogenicity was verified according to Koch’s rule. Species identification was performed based on colony morphology and molecular biological technologies. Effects of different carbon sources， nitrogen sources， temperatures， and pH on mycelial growth were determined using the single-factor method. Four aldehyde-based antimicrobial agents， salicylaldehyde， cinnamaldehyde， citral， and o-tolualdehyde， were selected to establish the toxic regression equations using the mycelial growth inhibition method， and the median effective concentration （EC₅₀） was calculated to evaluate antimicrobial effects.【Result】Five fungal strains were isolated from Annona atemoya with soft rot. Pathogenicity tests indicated that strain FLZ-1 exhibited the strongest pathogenicity， colonizing 80% of the fruit surface （diameter about 5 cm） at 10 d after inoculation of healthy Annona atemoya. Based on morphological and molecular biological identification， the strain FLZ-1 was identified as Aspergillus aculeatus. Biological characterization showed that the strain FLZ-1 exhibited the highest utilization rate of soluble starch as a carbon source and yeast extract as a nitrogen source， with optimal growth conditions at 28 ℃ and pH 6. The results of indoor virulence assay revealed that the inhibitory effects of the four aldehyde-based antifungal agents against strain FLZ-1， ranked from strongest to weakest， were： salicylaldehyde>cinnamaldehyde>citral>o-tolualdehyde. Salicylaldehyde had the lowest EC₅₀ value of 320.9046 mg/L. The slope in the toxic regression equations was positively correlated with the sensitivity of the pathogen to the agent； cinnamaldehyde had the highest slope （10.1284）， followed by salicylaldehyde （8.7489）.【Conclusion】The pathogen of postharvest Annona atemoya soft rot in Fusui County， Chongzuo City， Guangxi， is identified as Aspergillus aculeatus. Salicylaldehyde， a food-grade antimicrobial agent compliant with GB 2760—2024， demonstrates the strongest inhibitory effect against Annona aculeatus and thus is recommended as the primary agent for controlling postharvest Aspergillus aculeatus soft rot. Citral and cinnamaldehyde exhibit inhibitory effects but are less potent and may serve as alternative antimicrobial agent.