The belt of Palaeocene-Eocene copper-molybdenum porphyry deposits in southern Peru is an important part of the Andes metallogenic belt with a large number of world-class porphyry copper-molybdenum deposits. The recently explored Don Javier porphyry copper-molybdenum deposit is another major discovery in this belt. In this paper, studies of the petrology and geochemistry of ore-bearing porphyry and surrounding rocks were conducted to validate their petrogenesis and tectonic setting. According to major and trace element characteristics, the authors have reached some conclusions:① The ore-bearing porphyry belongs to peraluminous calc alkaline series dacite porphyry, the surrounding rocks belong to peraluminous calc alkaline series of granodiorite, and both have the same material source. ② The two types of rocks are enriched in light rare earth element and large ion lithophile elements; in chondrite normalized rare-earth element pattern, they show obvious right deviation type characterized by left steep and right slow, and both show Eu negative anomaly, which indicates that the petrogenesis of magmatic rocks involved crystallization differentiation or other geological processes. ③ The ore-bearing porphyry and surrounding rocks were formed in an an island arc environment, belonging to a classic rock island. ④ The Don Javier copper molybdenum deposit may have been formed in favourable conditions of the subduction of Nazca Plate to the South American plate, the melting of calc alkaline magma and the strike slip extrusion.