Abstract: By adjusting the ethylene contents in polypropylene for casting，a series of polypropylene copolymer was obtained. The effect of ethylene contents on the molecular weight and molecular weight distribution，mechanical properties，and crystalline structure of the resin was investigated. The ethylene sequence in the copolymer was characterized using 13C-NMR. It was found that the optimal ethylene contents was between 3.4 wt% and 4.0 wt%. When the contents of ethylene was 3.8 wt%，the impact strength and crystallinity of the copolymer reached 4. 7 kJ/m2 and 29.05 %，respectively.

Key words: ethylene contents, copolymcrizxcd polypropylene, casting film, sealing performance, crystallization performance