Polypropylene (PP) films with a high content of β crystal were prepared at crystallization temperatures (T c r ) of 20 and 110°C and then uniaxially drawn at different temperatures (T d r ). The drawn film prepared atT c r = 20°C had smaller pore volume and average pore radius than the one prepared at T c r = 110°C under similar drawing conditions (T d r = 130°C, draw ratio = 3.5-4.0). Electron microscopy revealed that most of the pores are formed by plastic deformation of the weak boundaries of lamellar blocks in the β-PP films. During drawing, the unstable β crystals in the film prepared at T c r = 20°C were easily deformed to undergo crystal transformation of β → α or β → smectic without much increasing the pore volume of the film. In contrast, the more stable β crystals in the film prepared at T c r = 110°C remained in the drawn film, and the micropores were enlarged. These results suggested that crystal transformation and micropore formation in the drawn films can be controlled by changing both T c r and T d r . The static and dynamic mechanical properties of the β-PP films were also measured to analyse the structural differences of samples of β-PP formed at different T c r .