<p>Ancient Chinese bronze mirrors, renowned for their artistic and cultural value, also serve as significant sources of scientific insight. Their corrosion layers present complex structures and diverse colorations, drawing interest from materials science, chemistry, and archaeology. This study analyzes twelve bronze mirrors from several museums and archaeological institutions using metallographic microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy to examine their internal corrosion structures. Analytical results indicate that the internal corrosion of bronze mirrors can be categorized into three distinct types: The first type is the most common, characterized by a smooth surface and preferential corrosion of the internal α-phase. The second type typically features a surface covered with corrosion products, exhibiting preferential corrosion of the internal δ-phase. The third type is the rarest; it also has an exceptionally smooth surface, but both the α-phase and δ-phase in the interior are completely corroded. The coloration of silvery, green, and black patinas on bronze mirrors is closely correlated with the type of corrosion and the oxidation degree of metallic soaps. When the corrosion of bronze mirrors is mild, the surface metallic soaps remain transparent, yielding silvery or green patinas. Conversely, in cases of severe corrosion, the heat generated during the corrosion process facilitates the oxidative coloration of metallic soaps, resulting in the formation of a black patina. Moreover, SnO₂ crystals appear on both the surface and the fracture sites of partially detached black patina fragments, indicating that the nanoscale SnO₂ crystals in the bronze mirrors form during natural corrosion processes. Notably, the formation mechanism of these nanoscale SnO₂ crystal films on the mirror surface strongly resembles the modern sol-gel technique used to prepare SnO₂ films.</p>