A superdrawn technique called crystal real drawing has beea applied to obtain the oriented isotactic polypropyIene (i-PP) films．Orystal mat of ultrahigh moIecular weight i-PP(Mw-4×106) obtained by crystallization from its dilute xylene solution，exhibits a dramatlcally high de-formability compared to both the low toolecular weight mat and the mek-crystallized forms．such cryatsl mats are prepared to a series of samples with the various draw ratios and the highest draw ratio can be achieved up to 69．An X-ray diffraction photograph shows that the c-axis of the lamellar crystals in the original mat orient preferentially in the normal direction of the mat plane，and such crystals had already been split and c-axis orientation had been turned to parallel with the draw direction in the draw ratio range of 110 and D040 decrease as the draw ratio is in-creased，but the long period L found to becomelarger with the draw ratio raise up to the high value．These results indicate that lamellar crystals are deformed through a chain folds unrave-ling and then partially recrganized into a fully straight crystalline structure．