The work aims to study the performance anisotropy of aluminum-plastic films and construct a mathematical model for strength of films with that of the substrate. The anisotropic characteristics and stress-strain behavior of each layer of aluminum-plastic film substrates were studied by tensile test. Based on the mixing law of laminated composites, the relationship model between the strength of aluminum-plastic films and the strength of substrates was constructed. The results showed that the lowest anisotropy index of strength of polypropylene films was 1.5, the lowest anisotropy index of elongation of nylon films was −0.8, and the anisotropy index of strength and elongation of aluminum foils were 4.0 and −8.7, respectively. Moreover, the anisotropy index of strength and elongation of aluminum-plastic laminated composite films was close to that of aluminum foils, which was the key substrate affecting the anisotropy of aluminum-plastic films. The stress model of aluminum-plastic films constructed based on the mixing law and linear regression analysis method is in good agreement with the actual results, indicating that it can be used as a reference for the selection of aluminum-plastic film substrates in the engineering field.