Garnet as one of the most typical and important skarn minerals in the Jiama super-large copper polymetallic deposit, Tibet, is a key point for study of skarn due to its wide distribution, various colours and strong mineralization. Through the numerous geological logging of rock/ore core and photo on its colour, crystal shape, mineral assemblage, mineralization, the feature of spatial distribution, mineralization, mineralogy and chemical composition of garnet have been concluded combined with the identification under microscope and electron probe analysis. Garnet in Jiama concentrates in the skarn and few in the hornfels, marble and porphyry close to the skarn. Garnet at Jiama is the andradite-grossularite series and andradite is the major garnet. There are colour and compostion zonations in garnet and it’s partially isotropic due to optical anomaly. The content of SiO2 and Al2O3 of the darker zones are higher than those of the lighter zones, whereas the TFeO content is opposite. Garnet formed at the earlier stage of skarnization, which is favorable for precipitation of sulfides of Cu, Mo, Pb, Zn, Au and Ag mineralization later. The features of mineralogy, component, REE, fluid inclusion and H-O isotope of garnet indicate its contact metasomatism genesis. Therefore, the Jiama ore deposit is a typical magma-derived hydrothermal contact metasomatism skarn type copper polymetallic deposit.