There are few reports on the occurrence of formate salts in the patina of brass buckles from clothing on a large-scale. Scientific methods, including super depth-of-field microscopy (DM), portable X-ray fluorescence spectrometry (pXRF), laser Raman spectrometry (Raman), and scanning electron microscopy-energy dispersive spectrometry (SEM-EDS) were employed to characterize the brass buckles and their patina from seven Qing Dynasty clothes. The results indicate that the buckles were precisely cast brass alloy, some of which were glided. The corrosion products were primarily composed of formate salts, including known compounds such as sodium copper formate [Cu₄Na₄O(HCOO)₈(OH)₂·4(H₂O)], dicoppertrihydeoxyformate [Cu₂(OH)₃HCOO], Zinc C [Zn₄Cu₃(Zn1-xCux)₆(HCOO)₈(OH)₁₈·6(H₂O)], as well as unidentified formic acid corrosion products containing Cl and S. The formation of these formate salts is related to the casting process of the brass buckles, the integrity of the gilding layer, and the storage environment. These corrosion products not only compromise the overall appearance of brass buckles, but also contaminate adjacent textiles and pronounced corrosive propagation. Therefore, the buckles need immediate corrosion removal, followed by wrapped with acid-free paper. This scientific analysis provides a theoretical basis for the development of conservation and restoration strategies for brass buckles on clothing, and serves as a reference for the study of similar cultural relics.