A low molecular mass PVC(LMPVC) was prepared by means of the combination of mechanical chemistry degradation and chemical degradation.The influence of technical condition on the properties of LMPVC and effect of LMPVC on the process properties of PVC were studied.It is proved that LMPVC has lower plastication temperature,higher melt fluidity and better compatibility with high molecular mass PVC.LMPVC can improve the plastication and the mechanical properties of the PVC resin.So LMPVC is a good processing aid.