Chitosan-based films exhibit green and biodegradable advantages in food preservation, but the brittleness and single function limit their practical applications. A multifunctional chitosan composite film and coating system was constructed using a deep eutectic solvent (DES) composed of glycerol and choline chloride as a plasticizer and CaCl2 as a crosslinker. It was found that when the molar ratio of glycerol to choline chloride was 1.5:1.0 and the Ca2+ concentration was 2%, the fracture elongation of the composite film reached 142.96%, and its light-shielding ability was significantly enhanced. Through immersion coating for preservation performance testing, the results showed that the coating treatment could effectively inhibit the weight loss of strawberries. By the 5th day of storage, the hardness and soluble solids maintained at a better level, and the time of mold spot formation was delayed by 2 days. Ca2+ formed a crosslinked network by coordinating with chitosan amino groups, synergistically enhancing film toughness with the hydrogen bonding effect of DES. Meanwhile, it activated the calcium/calmodulin-dependent protein kinase (CaM) signaling pathway in fruits, maintaining cell wall integrity. The rational design of chitosan films provides theoretical support and practical references for the development of green and efficient preservation materials.