Poly (butylene adipate-co-terephthalate) (PBAT)/starch composites have captured great attentions due to their favorable biodegradability and cost-effectiveness. However, it is still a challenge to prepare PBAT/starch composites with superior mechanical performance, solvent and creep resistance, and gas barrier. This study used a chain breaking-crosslinking strategy to prepare covalent adaptable network (CAN) composites from PBAT and unmodified starch via reactive extrusion. In the chain breaking stage, dipentaerythritol was used to break PBAT via transesterification and capped more hydroxyl groups on PBAT, achieving favorable compatibility with unmodified starch, which is confirmed via infrared spectroscopy analysis and scanning electron microscopy among other experimental methods. In the crosslinking stage, the hydroxyl groups of chain broken PBAT and starch were reacted with styrene-maleic anhydride copolymer (SMA) to form CAN composites. The superior compatibility and network feature gave the composites excellent thermal properties, strength and modulus, creep resistance, solvent resistance and gas barrier performance. Moreover, fast stress relaxation can be achieved based on the transesterification, allowing for extrusion processing and thermal compression molding, demonstrating excellent reprocessing recyclability of the PBAT/starch CAN composites. Overall, this work provides a simple, green and efficient method for preparing high-performance PBAT/starch CAN composites, which should also be suitable for other polymer/filler composites.