///This paper has studied petrographic, geochemical and zircon U-Pb chronological characteristics of gabbro and diorite from Qilesayi pluton as well as their tectonic significance. Geochemical analyses suggest that the gabbro has high Al₂O₃(13.47%~15.34%), FeOT(10.77%~16.89%) and moderate MgO(5.15%~7.49%) values, whereas the diorite samples are characterized by low SiO₂ content (52.06%~54.23%) and high Mg# values (58.63~62.45), belonging to the calc-alkaline series. Meanwhile, this study proposes that the gabbro and diorite from Qilesayi pluton were derived from the southward subduction of an oceanic crust to Milanhe-Jinyanshan active continental margin during the Early Paleozoic period, and this provides the corroborating evidence for the further ascertaining of the existence of the Early-Middle Ordovician continental margin arc.