Change of mechanical strength, thermal properties, and IR spectroscopy were studied for the ,γ, ray irradiation of isotactic polypropylene under various conditions, such as vacuum or air or at room temperature.,The change of crystalinity was calculated from the IR spectroscopy and the change of melting point was measured too. And the effects of storage time were compared.,For irradiation under vacuum, the G value of crosslinking and scission were calculated by measuring gel fraction as follows:,http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=42648947&type=,http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=42648949&type=,http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=42648948&type=,There was a significant decrease in the tensile break stress and strain of irradiated polypropylene in air for all doses but slight decrease in stress and strain of irradiated polypropylene in vacuum.