The mechanical properties of poly(vinyl chloride)/potassium titanate whisker(PTW),PVC/chlorinated polyethylene(CPE) and PVC/PTW/CPE composites,were studied here.Influences of CPE and PTW on the processability of hard PVC composites were also discussed here.The results showed that the mechanical properties of blends of PVC and PTW decreased compared with PVC itself.Synergistic effect on the toughening of hard PVC was observed when blending PVC,CPE and PTW within a certain mass ratio.PTW can increase the viscosity of the system and decrease the plasticizing time,while CPE on the opposite.