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Microstructures of as-cast and extruded ZK60-xRE (RE=Dy, Ho and Gd, x=0~5) alloys were investigated by optical microscope, scanning electron microscope, transmission electron microscope, X-ray diffraction and differential scanning calorimetry.Meanwhile, the impact toughness at ambient temperature was tested and then the relationship was discussed.The results show that the impact toughness value αnK increases from 9~17 J/cm2 for as-cast state to 26~54 J/crn2 for extruded state.With increasing the value of αnK, fracture macro-morphology changes from a rough plane via multi-plane with step to V-type plane with angle of approximately 120°, and from single radiation zone to two zones of fiber and shear lip, respectively.Fracture micro-morphology does from the brittle fracture to the ductile fracture.V-type impact fracture and micro-morphology are formed under the interaction of tensile and tear stresses.Fine grain and few fine dispersed second phase can enhance the impact toughness of magnesium alloys effectively.