The Weibao skarntype Cu-Zn-Pb polymetallic deposit, located at the junction of Xinjiang and Qinghai, tectonically belongs to the eastern part of the Qimantagh orogen. It comprises three ore blocks, referred to as Weidong, Main and Weixi respectively. The Weidong block is characterized by abundant Pb-Zn mineralization and minor Cu mineralization, while the Weixi block is characterized by abundant Cu-Pb-Zn mineralization. In this study, we carried out detailed research on the mineralogy of the skarn and ore samples from the Weixi block. On the basis of the mineral assemblages, ore structures and crosscutting relationship, the oreforming process of the Weibao deposit can be preliminarily divided into four stages, ie,the early skarn stage, the late skarn stage, the quartzsulfide stage and the quartzcarbonate stage, with the quartzsulfide stage being the main oreforming stage. Skarn minerals are mainly composed of garnet, pyroxene, epidote and amphibole, whereas sulfides mainly contain chalcopyrite, galena, sphalerite, pyrite and pyrrhotite. Electron microprobe analyses indicate that the garnet is compositionally predominated by andradite molecules (And=59.00%~97.70%) and grossular molecules (Gro=1.92%~40.42%), therefore belonging to the andraditegrossular series; pyroxene is predominated by diopside molecules (Di=45%~91%) and hedenbergite molecules (Hd=8%~53%), therefore manifesting as diopside and minor hedenbergite; amphibole belongs to the tremoliteactinolite series, although its composition varies greatly. Mineral assemblages and chemical compositions suggest that the skarn in the Weixi block is typical of calcic skarn. Moreover, the chemical components of garnet with zoning vary in a regular way that Al2O3 contents increase and then decrease while FeOTdecreases and then increases. The process shows metasomatism occurred along with change of pH in the oreforming fluid continuously from weak acidicalkaline to neutral condition and ultimately to weak acidicalkaline condition. High values of metals to sulfur in the sulfide of the Weixi block are higher than theoretical values, indicating that they likely formed in a high sulfur fugacity environment. In addition, sphalerite is characterized by the variable Fe and Zn contents (Zn=5450%~6475%, Fe=1.15%~10.16%), which might result from the fluctuation of oreforming temperatures and sulfur fugacities.