In this study, double-sided Al film was prepared on the surface of polyethylene terephthalate (PET) by controlling different Al target currents with magnetron sputtering technology. The micro-morphology of the Al film was observed using scanning electron microscope (SEM) and atomic force microscope (AFM). Phase analysis of the Al film was carried out using X-ray diffraction (XRD). The adhesion between the Al film and PET was detected by the cross-cut method. The light-blocking property of the Al film was measured by an ultraviolet-visible spectrophotometer. The transmittance of α and β particles in the Al film was detected using a handheld nuclear radiation detector. The results show that the surface of the Al film is smooth and flat with a metallic luster, and the Al grains are uniform and dense. The Al film has no defects such as pores and cracks. As the Al target current increases, the Al grain size, the thickness of the Al film, and the deposition rate all increase, and the roughness of the Al film first decreases and then increases. The light-blocking property of the Al film first improves and then decreases, and the average transmittance of both α and β particles gradually decreases. When the Al target current is 2.0 A, the roughness of the Al film is the minimum, which is 2.49 nm. The light transmittance is the lowest, around 0.025%. The average transmittance of α and β particles is the highest, being 581.7 CPS and 547.2 CPS respectively.