Abstract: To develop a new biodegradable antifungal packaging material, this study employed a casting method to prepare composite films using carboxymethyl chitosan and konjac glucomannan as film forming materials, with the incorporating varying proportions of crude protein extract from Bacillus velezensis T9. The morphology and chemical structure of the composite films were characterized using scanning electron microscopy (SEM) and fourier transform infrared spectroscopy (FTIR). The physical, chemical, antifungal and preservation properties of the composite films were investigated. The results indicated that the introduction of T9 crude protein increased the roughness and thickness of the composite films but reduced its tensile strength, water vapor transmission rate, and light transmittance (P<0.05). All composite films exhibited good environmental biodegradability, with degradation rates exceeding 90% within 20 days. With increasing concentrations of T9 crude protein, the composite films demonstrated significantly enhanced antifungal activity against Apiospora arundinis (A. arundinis) and a markedly increased inhibition rate on 3-nitropropionic acid (3-NPA) mycotoxin synthesis (P<0.05). When the T9 crude protein addition reached 0.12% (KCB12 treatment), the inhibition zone diameter against A. arundinis reached 20.5 mm, the lesion length on sugarcane decreased by 51.5%~65.0% compared to the control group (CK), and no 3-NPA toxin was detected. Furthermore, KCB12 treatment significantly reduced the weight loss rate (P<0.05), delayed the decrease in sugarcane juice pH, and maintained higher levels of soluble solids and sucrose content in sugarcane during storage. These findings provide a theoretical basis for the practical application of crude protein-based composite films from Bacillus velezensis T9 to control mycotoxin contamination and preserve the postharvest quality of sugarcane.