Abstract: Three types of nano-CaCO₃ filled powdered rubber composite particles were prepared by coagulation method using nano-CaCO₃ and latices as raw materials. The influence of the content of the composite particles on the mechanical properties of polyvinyl chloride (PVC) and their different reinforcing and toughening mechanisms were investigated. TEM micrographs show that the composite particles disperse well in the PVC matrix, where the nano-CaCO₃ particles exist either uncovered or embedded in the rubber continuum. It was demonstrated that all three composite particles can dramatically increase the notched impact strength of PVC, among which nano-CaCO₃ filled powdered acrylonitrile-butadiene rubber (CaCO₃-NBR) can achieve high stiffness and toughness. While nano-CaCO₃ filled powdered styrene-butadiene rubber (CaCO₃-SBR) improves the impact resistance at the cost of decrease in stiffness, resulting in the significantly decreasing of flexural modulus and tensile strength. The modification effect of nano-CaCO₃ filled powdered carboxylated styrene-butadiene rubber (CaCO₃-X-SBR) is between CaCO₃-NBR and CaCO₃-SBR. The results also show that the compatibility between the composite particles and PVC is the key point for the reinforcing and toughening effect. The composite particles with good compatibility with PVC matrix demonstrate better synergistic reinforce and toughen effect than the ones with bad compatibility.