The nanometer calcium carbonate (nano-CaCO3)-filled polypropylene (PP) composites were prepared using a twin-screw extruder, and the filler particle surface was pretreated, respectively, with fat acid (SI) and titanate coupling agent (SII) in this article. The notched and unnotched impact fracture properties were measured at room temperature by means of a Charpy impact instrument to identify the effects of the surface treatment and the filler concentration on the impact fracture properties. The results showed that the V-notched and U-notched impact strength slightly increased with an addition of the nano-particle volume fraction (I center dot (f)) for both two nanocomposites. When I center dot (f) was more than 10%, the V-notched impact strength of the system SII was obviously greater than that of the system SI, and the effect of surface treatment of the nanometer particles on the U-notched impact strength is insignificant. Furthermore, the impact fracture surface was observed by means of scanning electron microscopy to understand the relationship between the interfacial morphological structure and the impact fracture toughness of the PP nanocomposites.