Abstract: Nano-CaCO3 filled powder styrene-butadiene rubber was used to toughen polyvinyl chloride (PVC), the effect of the nano-CaCO3 content in compound modifier and the addition of the compound modifier on the mechanical properties of PVC was studied, and the impact fracture morphology was analyzed. The results show that the compound modifier could dramatically increase the notched impact strength of PVC. The maximum notched impact strength was 22.9 kJ·m-2 when the mass ratio of compound modifier to PVC was 15∶100 and the mass fraction of nano-CaCO3 in compound modifier was 70%, and a typical flexible fracture morphology was found on the fracture of the notched impact sample.