HMS(high Melt Strength) Polypropylene was manufactured by grafting bifunctional monomers, HDDA(1,6-hexanediol diacrylate) and TPGDA(tripropylene glycol diacrylate), under an electron beam irradiation. Complex viscosities in melt state of the modified polypropylene, which had been measured by means of ARES, were sensitive to the irradiated dose and the concentration of monomer. Complex viscosity at 190℃ of homopolypropylene modified by TPGDA could increase to 132290 pa·s from 5039 pa·s of homopolypropylene. The complex viscosity of modified polypropylene could be correlated with average molecular weights (M_w, M_n, M_z as the following equation: η^*=k_t (M_w/M_n)^α(M_z/M_w)^β.