The Subductionrelated porphyries on the southern margin of the Altay Mountains intruded in the Middle Devonian volcanic rocks of the Beitashan Formation. The main rock types include dioritic porphyry, quartz dioritic porphyry, granodioritic porphyry, and quartz monzonitic porphyry, etc. Representative porphyries from five copper deposits, i.e., Halasu, Kalaxiangeer, Kalasayi, Tuosibasitao and Qiaoxiahala, are chosen for geochemical analyses. Their geochemical data from the five deposits display somewhat similarity, and also somewhat difference. The SiO2 contents range from 534% to 662%, and A/CNK from 098 to 127, but most lower than 1. The trace element compositions are characterized by the enrichment of light rare earth elements (LREE) relative to high rare earth elements (HREE), and absence of Eu anomalies, MORB normalized inconpatible element patterns exibit significantly negative Nb and Ta anomalies. However, the Harker diagram and chondritenormalized REE patterns for these porphyries show that no regular variations can be recognized, which suggests that they were not derived from a common parental magma. The Sr and Nd isotopic compositions of the porphyries are close to those of the associated basalts (Beitashan Fm.), implying their genetic relation. Based on experimental petrology and REE modeling, it can be inferred that, they might be generated by partial melting of underplating basic rocks during arc evolution. The source regions are believed to be dehydrated amphibolite facies of lower crust, but minor garnet might be involved. The distinguished geochemical compositions of the porphyries from five copper deposits can be attributed to various ratios of garnet and amphibole in the source regions.