Located in Lapeiquan area, northern Altun Mountains of Xinjiang, the Qilesayi pluton consisting mainly of gabbro and diorite intruded into the Lapeiquan Group. 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%), FeO^T (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. The gabbro and diorite samples have features of low ΣREE content with low fractionation of LREE/LREE and no or slightly negative Eu anomalies, depletion of HFSE (Nb, Ta, Zr, Hf) and enrichment of LILE (Rb, Ba). These geochemical features imply an origin similar to that of the subduction-related tectonic setting. Zircon U-Pb ages obtained by LA-ICP-MS analyses from the gabbro and diorite samples are 477.5±3.3 Ma and 469.7±3.4 Ma, respectively, implying that these rocks were emplaced in the Early-Middle Ordovician period. Their petrogenic ages are similar to rock-forming ages of the adjacent Bashenkaogong gigantic phenocryst granitoid (474 Ma), Bashenkaogong-Xiemierbulake quartz diorite (481.6±5.6 Ma) and Jinyanshan granodiorite intrusive bodies (467.1±6 Ma), suggesting that they may be products of the same magmatism and constitute the basic-intermediate-acidic magmatic evolution series. Integrated with geochemistry, trace elements discrimination, geochronology and regional background, it is inferred that that the gabbro and diorite were formed in a subduction-related active continental margin arc. 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 and subduction polarity of Hongliugou-Lapeiquan ophiolite mélange zone in the North Altun Mountains.