Abstract: The Hongdoushan granite porphyry in the South Langcangjiang volcanic arc zone is a peraluminous and shoshonite Stype granitoid. The granite porphyry contains 71.1%~74.4% of SiO₂, high total alkalis (K₂O+Na₂O=8.4%~9.4%), high K and high A/CNK of 1.06~1.21, and is characterized by enrichment of light rare earth elements with negative europium anomalies (δEu=0.53~0.74), relative enrichment of large ion lithophile elements (LILE) such as Rb, Ba, Th and U, and relative depletion of Sr, P and Ti. Geochemical features indicate that the Hongdoushan granite porphyry has characteristics of volcanic arc granite and syn-collision granite, and is epicontinental arc-volcanic rock. LA-ICP-MS zircon U-Pb dating age of the Hongdoushan granite porphyry is 220.3±3.6Ma, indicating that the rock was formed during Late Triassic. Geochemical features and formation age of the Hongdoushan granite porphyry is very similar to features of basic volcanic rock of Xiaodingxi Formation, which suggests that they are products of different stages of the same magmation.