Poly(adipate butylene-to-terephthalate)/Poly(lactic acid) (PBAT/PLA) blends were prepared by melt blending method used aluminate coupling agent (ACA) as compatibilizer. Effects of ACA contents on the structure and properties of PBAT/PLA blend system were investigated by FT-IR, melt indexer, differential scanning calorimeter, rotational rheometer, dynamic mechanical thermal analyzer, SEM and servo control tensile testing machine. The results showed that ACA interpenetrated between PBAT and PLA molecular chains, causing physical entanglement with PBAT and PLA, increasing intermolecular distance, improving molecular chain compliance, and enhancing the force between PBAT and PBAT. The compatibility of the two phases was improved, and the tensile toughness of PBAT/PLA/ACA blend was increased. The elongation at break of PBAT/PLA/ACA blend was increased from 250.9% to 410.7%. The ACA has a remarkable plasticizing effect, which increased the melt mass flow rate, storage modulus and loss modulus and complex viscosity and the glass transition temperature of PBAT and PLA of the blended system was reduced, and the crystallinity of PLA in the blend system increased from 18.8 % to 26.6 %.