To investigate the effects of acidic calcium sulfate (ACS) treatment on black mold infection and storage quality of gray jujube, in vitro assays were conducted to evaluate the inhibitory effects of ACS on Aspergillus niger colony growth, spore germination, and mycelium development in Xinjiang gray jujube. Further, in vivo vacuum-impregnation treatments were performed to examine their effects on the storage quality parameters of gray jujube. The results showed that ACS treatment had a significant inhibitory effect on A. niger colony formation, spore germination, and mycelial development, with ACS-10-1 (10 000 mg•L-1) exhibiting 100% inhibition in all cases. Scanning electron microscopy showed that ACS significantly disrupted the microstructure of A. niger. ACS could effectively reduce the incidence of black mold infection in grey jujube. Compared with the CK group, ACS-10-1 exhibited 100% inhibition. Vacuum impregnation with ACS also significantly reduced natural decay, slowed moisture loss, maintained total soluble solids, titratable acid (TA), and ascorbic acid (AsA) levels, and decreased surface microbial counts. After 60 days of storage, natural decay was 39.29% lower in the ACS-treated group than in the CK group; moisture content and TA and AsA levels were 3.14%, 8.13% and 2.54% higher, respectively, and total colony counts as well as mold and yeast counts decreased by 1.13 and 1.43 log10CFU/g, respectively. In summary, vacuum impregnation with ACS is a safe and effective postharvest sanitizing and preservation method for gray jujube. The results provide a theoretical basis for quality preservation technology in the Xinjiang gray jujube industry.