Mechanical properties have close relation with microstructure. Based on orientation of the molecule chain in fiber, they show a rapid increase in tensile properties. Nevertheless, block materials mainly gain rise of mechanical properties by blend or composite, it is hardly proposed on the self-reinforced materials by optimizing the microstructure. In this paper, a strengthening of PP was gained by uniaxial compression through small deformation of spherulite. A series of measurements were applied, including tensile test, polarizing optical microscope (POM) and differential scanning calorimeter (DSC). The results show that the tensile properties of polypropylene (PP) have a rapid rise. POM suggestes that the spherulite has deformed into ellipsoid even belt along the orientation of sample of PP, which plays an important role in self-reinforcing of PP. And the initial melt point displayed by DSC slightly decreases because of the partial ruptures of crystal phase.