The Properties of polypropylene film and nonwoven, such as the viscosity average molecuar weight, degree of tacticity and mechanical strength have been ivestigated by irradiation in vacuum, in nitrogen. and in air at room temperature.,The gases evoluted during irradiation have been analyzed and meas measured, so that the G values were calculated as foollows: 2.52~3.56 for H,2, 0.11~0.12 for CH,4, 0.01~0.02 for ,C,2, H,4, 0.13~0.20 for C,3, H,6, and 0.24~0.26 for C,4,H,8,.,The results showed that the physical and mechanical prorerties of polypropylene were not changed, when the dose of radiation was lower than 5×10,5, rad, but decreased with fourther increasing doses (up to 5×10,6, rad) and a large quantity of low molecular hydro-carbon compounds were produced, When the dose exceeded 3×10,7, rad, the polypropylene sample could be dameged extremely and even changed into powder.,It was found by the ESR measurement that trapped free radical of polypropylene, irradiation in vacuum at room temperature, was converted into peroxy radical rapidly as the samples were exposed in air, obviously, this may cause auto-oxidation degradation of polypropylene,The authors suggest that in order to improve the radiation stability of polypropylene it is necessary to add some anti-oxidents or to prepare polypropylene in the form of multi-component copolymers.