Abstract: The synergetic toughening effect of nitrile rubber (NBR), CaCO3, and acrylonitrile-butadiene-styrene copolymer (ABS）for chlorinated polyvinyl chloride (CPVC) was studied. When the contents of NBR and ABS were 5 and 4.5 phr, respectively, an impact strength of 74.1 kJ/m2 was obtained, which was 2.5 and 4.4 times those of the systems containing NBR or ABS alone. Optical microscopy showed that core-shell NBR phase dispersed very well. SEM micrographs indicated that the impact fracture of CPVC toughened with NBR and ABS mainly followed the ductile failure.