The composition, migration and evolution of hydrothermal fluids as well as the precipitation mechanism are the essence and main difficulties in the study of hydrothermal deposit. Skarn deposit has long been one of the most important hydrothermal deposits in that hydrothermal fluid in this kind of deposit has complex evolution process with multiple stages. Diopside and garnet are the most typical minerals in skarn deposit. Garnets with oscillatory zoning have recorded the property, composition and evolutionary process of the fluids completely in skarn deposits, which suggests that the compositions of garnets of different series have a specific selectivity for physical and chemical environments of hydrothermal fluids at different stages. Chemical elements zoning of gar_ net result from periodic emersion between fluid mobility and mineral reprecipitation, which could indicate the mechanism of major and trace elements zoning in prograde skarn fluid. The values of Fe₂O₃ and Al₂O₃ in differ-ent garnets vary remarkably, which plays an important role in tracing redox environment at the process of fluid evolution. In addition, trace elements constitute a more sensitive probe for detecting fluid evolution to some extent, which could reflect an important process in petrogensis and metallogeny. The grossular is often enriched in Al, Ti, Zr and HREE; however, the andradite is enriched in As, W, Mo, Fe and LREE. In-situ electron microprobe analysis and LA-ICP-MS technology have played an important role in major and trace elements(including REE)analysis of garnets having oscillatory zoning in the process of ore-forming fluid evolution, which can reveal garnets growth mechanism, ore-forming environment and fluid property.