XRD and XRF were used to identify several brass coins of Qing dynasty collected in the Ezhou Museum and excavated from Ezhou of Hubei province. The reality of the coins contains 36. 53%-37.75% of Zn, 54. 12%-59. 04% of Cu and 3. 51%- 7. 56% of Pb, and the ration of the alloy is steady and scientific, indicating that the technic of the alloy of brass was quite perfect in the mid to late of Qing dynasty. Zn3Cu2 (OH)6 (CO3)2 was found in the corrosion for the first time, and CuO, ZnO, Fe2O3 and CuCI were found too. The high content of Cl^-, around the local condition (including the polluted environment), may be the main reason for those brass coins to be eroded seriously. These findings provide some reference for collecting and protecting coins.