In this study, a serious of super-toughened poly (lactic acid) (PLA)/cross-linked polyurethane (CPU) blends were prepared via one-step dynamic vulcanization of PLA, polyethylene glycol (PEG) and isophorone diisocyanate trimer (IPDIT). FTIR and gel tests displayed that CPU was successfully generated during the dynamic vulcanization reaction. The scanning electron microscopy (SEM) images of cryo-fractured and impacted surfaces showed that the PLA/CPU blends had no obvious phase separation, which indicated good compatibility between PLA component and obtained CPU component. It also revealed the toughening mechanism dominated by shear yielding. The DSC results show the crystallinity of all the PLA/CPU blends were higher than neat PLA, indicating the CPU component can act as a crystallization nucleating agent for PLA component. When the PEG content is 30%, the impact strength and elongation at break of PLA/CPU blends can be increased to 35 times and 42 times, respectively. All the results indicate the interfacial reaction and compatibilization between the PLA and CPU resulted in the formation of super-toughened PLA/CPU blended materials.