Electrons-irradiated homo-polypropylene(HPP) and random ter-polymer of propylene(RTPP), in which trifunctional monomers such as trimethylopropanetriacrylate(TMPTA) or triallylcyanuate(TAC) was added as crosslinking agent, showed comparably high degree of crosslinking: wherein the maximum degree of crosslinking was 67% and 52% around at 5 kGy for HPP and for RTPP, respectively, both added with TMPTA, whereas the degree of crosslinking in HPP with TAC continuously increased with radiation dosages, reaching to 65% at 240 kGy. From several experimental data such as, gel content, melt index, swelling ratio, and average molecular weight distribution, HPP with TAC and RTPP with TMPTA were found out to be much higher radiation-stable than HPP with TMPTA, especially at high dosages. The heat of fusion data could show that radiation crosslinking hardly gave an effect on changing of crystallinity in the irradiated polypropylene and could occur mainly at boundaries between crystalline and amorphous phases. It was found that HPP added with more than 2 mmol% of TMPTA were difficult to be highly crosslinked probably due to a homopolymerization by an excess of this monomer.