Poly (butyleneadipate-co-terephthalate) (PBAT) was used to toughen poly (lactic acid) (PLA), and a fully biodegradable high impact PLA/PBAT composite was prepared. To improve the interface compatibility between PBAT and PLA, PBAT grafted glycidyl methacrylate (GMA)(PBAT-GMA) compatibilizer was prepared by the melt grafting method. The effect of the mass fraction of compatibilizer on the properties of PLA/PBAT composite was studied. The results show that with the increase of PBAT-GMA mass fraction, the impact strength of the composites is significantly improved. When the PBAT?GMA mass fraction is 30%, the impact strength of the composites reaches 64.8 kJ/m², and the elongation at break is 289.9%; the compatibilizing mechanism is the epoxy groups on PBAT?GMA can react with the end groups of PLA, which effectively improves the interfacial compatibility between PLA and PBAT.