Abstract: High-melt-strength polypropylene with long chain branching structure(LCB-HMSPP) was prepared by 60Co-γ ray irradiation in the presence of bi-functional monomerGttfert Rheotens extensional rheometer was used to characterize extensional rheological behavior of this LCB-HMSPPThe effects of sensitizer content, radiation dose, adding a small amount of high molecular weight component, as well as temperature were investigatedIt was indicated that melt strength, extensional stress and transient extensional viscosity were prominently enhanced after 60Co-γ ray irradiation. In addition, these extensional parameters increased with increasing sensitizer contentMelt strength, extensional viscosity reached a maximum when radiation dose approximately equaled to 5kGyAdding a small amount of ultra high molecular weight polyethylene(UHMWPE) could also play an important part in enhancing the extensional rheological behavior of PPThe activation energy of melt strength decreased with increasing sensitizer content and by adding a small amount of UHMWPELCB-HMSPP showed less temperature sensitivity than linear PP, and exhibited high melt strength, high extensional viscosity in a broad range of temperature.