<p>Poly(butylene carbonate) (PBC), a biodegradable aliphatic polycarbonate, is limited by its suboptimal thermal and mechanical properties. This study enhanced PBC by incorporating nanoscale nucleating agents combined with isothermal annealing and pre-stretching. The results indicate that the dispersion and interfacial interactions of different nucleating agents within the PBC matrix vary significantly. Among them, SiO₂ demonstrate good dispersion and compatibility, effectively enhancing the storage modulus and crystallization kinetics. Isothermal annealing and pre-stretching treatments further synergistically improved the crystallinity and mechanical performance of the composites: after annealing, the tensile strength of PBC/SiO₂ increased to 61.96 MPa, and after pre-stretching, it reached 83.26 MPa. Dynamic mechanical analysis and differential scanning calorimetry results consistently show that the incorporation of nucleating agents raises the glass transition temperature and thermal stability of the materials. This research provides systematic experimental evidence and process optimization strategies for the high-performance modification of PBC.</p>