PLA is widely used in the field of disposable products for its good transparency, high strength, high modulus, and good processing performance. However, the crystallization rate and crystallinity of PLA are weak. In actual production, the PLA products that are typically obtained are amorphous with poor heat resistance, which greatly limits the application range of PLA products. Finding an effective nucleating agent to improve the transparency of PLA has been a hot topic in research. This study found that Cerium fluoride (CeF₃) can effectively improve the crystallinity of PLA/CeF₃ (P/F) films. When the content of CeF₃ in PLA was 1 wt %, the retention ratio of visible light transmittance was 82.36%, the crystallinity was 29.8%, and the tensile strength was 59.92 MPa. Compared to pure PLA, the crystallinity of P/F1 increased by 56% and tensile strength increased by 8.76%. This study provided an alternative scheme that maintained the PLA film’s transparency and improved the crystallinity of PLA, which significantly expanded the application of PLA.