The J-integral method was introduced to investigate the fracture process of PP/CaCO3 composites. The results showed that the resistance of PP/CaCO3 composites to crack initiation and propagation was greatly improved with the addition of CaCO3 filler. Large scale plasticity was caused in PP/CaCO3 composites, from which a large amount of energy was absorbed by the PP matrix. The reason for the increase in the fracture toughness of PP/CaCO3 composites was attributed to the partial micro-drawing ahead of the crack tip in the PP matrix, which was formed by the stress concentration caused by the filler particles in the PP matrix and/or by the interfacial debonding between filler particles and the PP matrix. It was indicated that the presence of CaCO3 filler could augment the ductility of composites locally, resulting in higher fracture energy in the crack initiation and propagation of the PP/CaCO3 composites in a certain CaCO3 content range.