Abstract: The differences and the characteristics of the dynamic mechanical resonances between dynamic vulcanized and unvulcanized PP/EPDM blends with deffrent content of EPDM were studied by means of the dynamic mechanical analysis. The results showed that, compared with the unvulcanized PP/EPDM blend, the dynamic vulcanized PP/EPDM has the characteristics of smaller Tg larger mechanical loss peak width, higher mechanical loss strength and lower mechanical loss peak temprature at the room and low temprature, a change in the peak value of the mechanical loss at 6070 and some appearances of and secondary transition under the transition (Tg) of EPDM etc. The main reason why the toughning effect of the dynamic vulcanized PP/EPDM blend was better than the unvalcanized PP/EPDM blend is that, the dynamic vulcanized PP/EPDM can increase the compatibility between the two phases PP and EPDM, increase the mobility of the molecular segments and form the new chemical structures which can have the mobility at the low t emprature etc. From the results it can be also predicted that the dynamical vulcanized PP/EPDM blends may have the advantages of the high cold properties and high holding ratio of the modulus at the high temprature.