In this article, two β nucleated polypropylene (β-iPP) precursor films were prepared through crystallizing at 110 and 135°C. The differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), scanning electron microscopy (SEM) and tensile testing were employed to investigate the influence of annealing on stress-strain behaviors and performances of biaxial stretched membranes. The traditional time consuming annealing treatment demonstrates that within the most favorable annealing temperature window of 130-140°C, only a small fraction of thin β lamellae melted and recrystallized to form more stable β phase, resulting in the slight improvement of the stress-strain behaviors and performances of β-iPP membranes. Furthermore, a rapid annealing method was designed, involving a short time thermal stimulus at high temperature and then cooling in the air. During this process, substantial melting and epitaxial crystallization of less stable β crystal occurred, leading to the apparent thickening of β lamellae and the narrowing of β lamellar thickness distribution. Consequently, the stress-strain behaviors of β-iPP films and performances of biaxial stretched membranes were improved significantly.