Green biodegradable bio-based films have gained interest in replacing petroleum-derived plastic packaging materials as a new preservation strategy for fruits and vegetables to alleviate environmental pressures. In this study, we aimed to develop novel biodegradable composite films based on microcrystalline cellulose (MCC) reinforced polylactic acid (PLA). Our results demonstrated that the addition of 3% MCC to PLA could improve its tensile strength. Scanning electron microscopy analysis revealed that MCC dispersed well in PLA at lower content while agglomerated at higher content. It was discovered that all four types of MCC/PLA biocomposite films could retard the color change of Lanzhou lily bulbs, accompanied by maintaining favorable total soluble solid, total sugar, total polyphenols, and flavonoid content, inhibiting the activities of phenylalanine ammonia-lyase and the content of malondialdehyde during storage. Moreover, the preservation effect of MCC/PLA biocomposite films on Lanzhou lily bulbs was evaluated using a membership function, and the SSS MCC/PLA biocomposite film demonstrated a favorable fresh-keeping effect. In conclusion, four types of MCC from different biomass materials added to PLA-based products can be beneficial in improving the attractive properties of biocomposite films. These films are expected to replace petroleum-derived plastics as a new packaging material for preserving Lanzhou lily bulbs.