The Yangla Cu deposit is the largest Indosinian Cu deposit in the middle segment of the Jinshajiang suture zone. The ore bodies are mainly developed in the periphery of the granodiorite and between carbonate and metamorphic sandstone with stratiform- like shape. Its genesis has been debated for decades with ideas including sedimentary exhalative, skarn, and superimposed models. In this contribution, garnet U- Pb age and the composition of garnet and magnetite were determined to further define the timing and genetic type of this deposit. The analysis showed that the garnets have U, Th and Pb contents of 1. 18×10-6~6. 69×10-6, 0. 04×10-6~1. 43×10-6, 0. 11×10-6~1. 16×10-6, respectively, and yielded an intercept age of 231. 0±5. 3 Ma (2σ, n=32, MSWD=2. 1). This represents the timing of skarn formation coeval with the generation of granodiorite. In combination with magnetite showing compositions similar to skarn deposits around the world, it is confirmed that the Yangla is a typical skarn Cu deposit. Garnets belong to andradite and are mainly characterized by enriched LREE and depleted HREE, which was controlled by both crystal chemistry and adsorption. In combination with their high Eu positive anomalies and low U concentrations, it is suggested they formed in a slightly low pH, enriched Cl, and relatively oxidized environment. Compared with other Cu skarn deposits worldwide, garnets at Yangla contain significantly higher Sn (485×10-6~7433×10-6, average 3931×10-6) and W (0. 20×10-6~736×10-6, average 156×10-6), and magnetites also have higher Sn (115×10-6~778×10-6, average 405×10-6). This is similar to the characteristics of W- Sn skarn deposits around the world. Combined with garnet U- W and Sn- U diagrams, it is proposed that W and Sn mineralization may have developed in the ore field.