Abstract: Garnets preserved in calc-alkaline volcanic rocks can not only constrain the temperature and pressure conditions of magma crystallization, but also can reveal the evolution history of the host magma, presenting significant genetic implications. However, garnet occurring in calc-alkaline volcanic rocks is extremely rare globally, and there remain substantial controversies regarding the genesis of such garnets. In the Jurassic garnet-bearing dacite from Xishan complex, three genetic types of garnet crystals coexist: magmatic garnet, metamorphic garnet and peritectic garnet. Magmatic garnets mostly occur as single crystals without reaction rims, characterized by low MgO (0.92～2.37%), CaO (1.21～2.85%), and MnO (0.82～1.64%) contents, but high FeO (36.01～39.82%) contents. Metamorphic garnets develop albite reaction rims. In terms of composition, they are rich in MgO (7.42～8.46%) and FeO (27.80～30.99%), and poor in CaO (1.32～1.33%) and MnO (0.56～0.60%). For peritectic garnets, the contents of MgO (2.89～3.55%), FeO (34.57～37.39%), CaO (2.08～2.51%), and MnO (0.72～1.17%) are all between those of the former two types. In terms of rare earth elements (REE), all three types of garnet exhibit strong depletion in light REE(LREE). Notably, magmatic garnets are enriched in heavy REE(HREE), with the most significant Eu negative anomaly (Eu/Eu^*=0.004～0.005). Metamorphic garnets are depleted in HREE,and the total rare earth element content (∑REE=64～72ppm) is significantly lower than those of the magmatic garnets (∑REE=681～906ppm), with a weaker Eu negative anomaly (Eu/Eu^*=0.24). The characteristics of rare earth element of peritectic garnets are generally between those of magmatic and metamorphic garnets (∑REE=673～2731ppm; Eu/Eu^*=0.02～0.03), and the content variation range is relatively large. Petrographic and mineral chemical characteristics consistently indicate that the magmatic garnets in the garnet-bearing dacite from Xishan complex is a product of early crystallization during magma evolution under high-temperature (740～959℃), high-pressure (>7kbar), and low oxygen fugacity (logfO₂: -23.67 to -12.32) conditions in the lower crust. In contrast, the metamorphic garnets are metamorphic crystal captured from the source rock by volcanic eruption after the former crystallized. The peritectic garnets were formed by partial melting of biotite dehydration during the decompression partial melting process of metapelitic rocks in the lower crust of the study area. Combining with the regional geological context and Hf-O isotopic characteristics of zircon and garnet, this study suggests that the Xishan garnet-bearing dacite may be derived from relatively mature metasedimentary rocks and formed in an extensional tectonic setting.