The blends of recycled high density polyethylene (RHDPE)/home-made complex toughening agent (CTA) were prepared by a twin-screw extruder. The effects of CTA contents on mechanical properties, melting and crystallization behavior, thermal properties and microstructure of blends were studied. The results showed that the impact strength was significantly increased with the increasing content in CTA, while the elongation and tensile strength decreased. The toughening effect obviously slowed down when CTA content was over 20%. The results of DSC and TGA displayed that there was no obvious effect on the degree of crystallinity as well as thermal properties of RHDPE , but the integrity of PE crystal structure was lowered after CTA was added to RHDPE. The SEM results showed that the toughness of the blend was significantly improved, but the effect slowed down with poor dispersion and agglomerates when CTA content exceeded 20%.