Pre-irradiation grafting of poly NIPAAm on silicone rubber was completed successfully. It was found that the graft reaction could be done just at higher temperature and induced by peroxides (mainly hydrogen peroxides) produced during irradiation of samples in air. Production and decomposition of the peroxides were investigated. The active energy of peroxides decomposition equals to 27.2 kJ/mol. The study of grafting kinetics showed that the graft reaction is easy to occur at higher temperature because of the active energy of graft reaction was low,near to 54.7kJ/mol. And the grafting mechanism was discussed deeply.