Strontium-aluminates-based phosphorescent composite films were prepared by homogeneously distributing the green light emitting phosphors within polystyrene hosts. The composite films have the unique properties of flexibility of the polymers and the long-lasting phosphorescence of the strontium-aluminates-based phosphors. The microstructures of the flexible composite films were characterized with scanning electron microscopy. The results indicated that the organic and inorganic materials can be combined with each other better, and the composite films can be easily rolled but will not generate cracks. Therefore, this composite technology can effectively enhance the moisture resistance of the phosphors and the films can be used in the filed of information display.