Abstract: The PP/EVA/nano-SiO2 composites were prepared by melt blending, in which the nano-SiO2 was surface-treated with EVA, and then, a surface-modified BOPP film was prepared by using the resulting composites. The surface morphology and cross-section of the film were observed by scanning electron microscopy, and their degree of crystallinity, molecular orientation and grain size were detected by X-ray diffraction measurement. Furthermore, the presence of microholes in the film was confirmed by positron annihilation spectroscopy, and the relationship between the crystalline structure and morphology and the solvent residue was investigated. The results indicated that the modified BOPP film not only had a higher degree of crystallinity and smaller grain size than the unmodified one, but also had a dense surface structure and reticular fiber bundle internal structure. These characteristic structures make the diffusion coefficient and solubility of ethyl acetate small in the film, thus improving the mechanical properties significantly.