To explore preparation method of citrus postharvest antifungal film, konjac glucomannan/curdlan-Bacillus sp. w176 fermentate (KCB) composite films were fabricated by combining natural polysaccharides with antifungal fermentate. The supernatant of w176 was subjected to vacuum freeze-drying to collect solid fermentate. The fermentate was combined with the polysaccharides to prepare composite solutions which was then cast and dried to form films. The w176 fermentate contained the Bacillus cells and its antifungal metabolites. The agar diffusion method for antimicrobial testing indicated that both the w176 fermentate and KCB composite films exhibited significant antifungal effects against Penicillium digitatum P44 and Penicillium italicum B3. The results of structural and property tests of the composite films showed that the surface and cross-sectional structure of the KCB composite films were continuous, uniform, and dense, with good compatibility between antifungal components and polysaccharides through non-covalent bonding. The w176 bacteria were uniformly distributed in the polysaccharide network. However, due to the hydrophilic nature of the antifungal components in the fermentate, the addition of w176 fermentate weakened the water resistance and mechanical properties of the composite films. The dissolution ratio (25.35%), water contact angle (71.7°), tensile strength (36.54MPa), elongation at break (8.86%), and water vapor and oxygen transmission rate (3.12kg·m-2·d-1 and 4.89g·m-2·h-1) of the KCB-5 composite film with a w176 fermentate concentration of 0.05g/L were significantly superior to other composite films. Comprehensive performance indicated its applicability for post-harvest preservation of citrus fruits. The antifungal experiment showed that KCB-5 composite film significantly inhibited the pathogenicity of pathogens B3 and P44 in postharvest preservation of citrus, which was of great significance to the citrus postharvest preservation industry.