Abstract: Three measurement methods for crystallinity of three kinds of isotactic polypropylene,i.e. homo-polypropylene (PPH),ethylene-propylene block copolymer (PPB) and ethylene-propylene random copolymer (PPR),were introduced by different scanning calorimeter (DSC),wide angle X-ray diffractometer (WAXD) and density gradient test. The reason of different results was also analyzed. The results showed that,although there was an a significant difference among three kinds of method,the sequence of crystallinity of different isotactic polypropylene was the same,i.e.,PPH>PPB>PPR. And at the aspect of sensitiveness in characterizing crystallinity of different kinds of polypropylene,DSC was better than WAXD,and the density gradient test had poor appearance.