To make crosslinked polypropylene (PP) and PP with high melting strengths, we studied the effects of radiation on the crosslinking and branching of PP in detail with the Charlesby-Pinner (C-P) equation. We studied the radiation crosslinking and branching behavior of homopolypropylene (HPP), impact copolypropylene (IPP), and random copolypropylene (RPP) and used the C-P equation for some parameter calculations. We found that (1) the C-P equation seemed applicable when PP with a multifunctional crosslinking agent was irradiated within a certain dose range in air and (2) IPP had the highest gel dose value, crosslinking G value/scission G value, and gel fraction after irradiation among HPP, RPP, and IPP; therefore, IPP is the best material for making radiation crosslinking and radiation branching PP among HPP, RPP, and IPP.