The polycaprolactone (PCL)-b-polyethylene glycol (PEG) oligomer (Oli) and its derivative containing ionic elements (ILs) were used as interfacial compatibilizers and regulators, and the polylactic acid (PLA)/PCL/Oli and PLA/PCL/ILs blends were prepared by solution blending. The effects of Oli and ILs on the phase interfacial properties, aggregated structure, crystallization and mechanical properties of PLA/PCL blends were systematically studied. The results show that the ILs with strong interfacial emulsification ability can improve the dispersion of PCL in PLA matrix, and enhance the two-phase interfacial adhesion. When the content of ILs is 5 %, ion clusters can form and alleviate the restricted crystallization of PCL, and promote the segment movement of PLA through the non-covalent bonding of ionic elements. So the crystallization ability of PLA and PCL improve simultaneously. ILs have a strong regulatory effect on the phase interfacial morphology and aggregated structure of PLA/PCL blends, and the PLA/PCL blends containing high content of 5 % ILs can significantly improve the mechanical properties of PLA/PCL blends.