To enhance the value-added utilization of pomegranate peel byproducts and develop safe and effective natural skin-whitening active ingredients, this study used pomegranate peel as the raw material to extract and purify its polyphenolic components. The study systematically evaluated their tyrosinase inhibitory activity and mechanisms of action, while also constructing a bilayer emulsion delivery system to improve stability and assess application performance. The results indicate that LX-17 macroporous resin exhibits superior purification performance for pomegranate peel polyphenols; under conditions of a loading concentration of 1.226 mg/mL, pH 3, a loading rate of 0.9 mL/min, anhydrous methanol as the eluent, and an elution rate of 0.9 mL/min, the purity of the pomegranate peel polyphenols increased significantly from 22.15% to 66.62%. HPLC results confirmed that the main component was punicalagin, with a content of 826.28 mg/g after purification. The purified polyphenols exhibited good tyrosinase inhibitory activity, primarily through a combination of steric hindrance, induction of enzymatic conformational changes, and chelation of active copper ions to achieve mixed-type inhibition of tyrosinase, while simultaneously eliminating key intermediates such as dopaquinone, thereby exerting a dual inhibitory effect. To improve the stability of the polyphenol, a bilayer emulsion delivery system was constructed and its melanin synthesis inhibitory activity was evaluated. The results showed that a 0.9 μg/mL purified polyphenol bilayer emulsion reduced the relative tyrosinase activity in B16 cells to 69.79%, and the relative intracellular melanin content dropped sharply to 64.24%. Its melanin synthesis inhibitory activity was significantly superior to that of the positive controls, kojic acid and free polyphenols (P < 0.05). These findings provide a theoretical basis and practical reference for the development of natural skin-whitening active ingredients from pomegranate peel and their application in functional cosmetics.