The northern Sanjiang porphyry Mo(-Cu) ore belt is located in the southern Qinghai Province, where a series of NE-SE trending Cenozoic Mo-Cu mineralized rock bodies occur. In recent years, lots of large-size porphyry-skarn Mo(-Cu) oren deposits, such as the Narigongma porphyry-type Mo(-Cu) deposit and the Lurige and Dagugongka porphyry-skarn-type Mo(-Cu) lead-zinc deposits have been discovered. Based on analyzing petrologic characteristics of element geochemical data and Sr-Nd-Pb istopic data of representative porphyries in Narigongma, Lurige and Dagugongka, this paper discusses the metallogenic geological background and the origin and evolution of porphyries in the study area, with the purpose of contributing to future mineral exploration. Ore-bearing porphyries in the study area are mainly biotite granitic porphyries and leucogranitic porphyries, with SiO₂ content of 64.87%～76.30%, K₂O+Na₂O 3.43%～8.90%, and K₂O+Na₂O 0.79%～47.24%, belonging to the calc-alkaline-shoshonitic series and being similar to things of the Yulong mineralization belt. All the ore-bearing porphyries in the study area have similar distribution of rare earths and trace elements, with right-oblique curve, characterized by LILE (large-ion lithophile element) concentration, high field strength elements depletion, and significant Ti-Nb-Sr trough. The porphyries show weak Eu-depleted anomaly and adakite affinity. The ²⁰⁶Pb/²⁰⁴Pb ratio ranges from 18.410 0 to 19.429 0, ²⁰⁷Pb/²⁰⁴Pb from 15.609 0 to 15.685 0, ²⁰⁸Pb/²⁰⁴Pb from 38.577 0 to 39.522 8, ⁸⁷Ru/⁸⁶Sr from 1.901?0 to 8.722, ⁸⁷Sr/⁸⁶Sr from 0.705 291 to 0.710 307, (⁸⁷Sr/⁸⁶Sr)_i from 0.702 873 to 0.705 859, and ¹⁴³Nd/¹⁴⁴Nd from 0.512 573 to 0.513 204, and the depleted mantle age (t_DM) is 0.60～0.85 Ga. These data are basically consistent in all the ore deposits. Most of ²⁰⁷Pb/²⁰⁴Pb-²⁰⁶Pb/²⁰⁴Pb are distributed in enriched mantle (EMⅡ). (⁸⁷Sr/⁸⁶Sr)_i-εNd(t)values are on the evolution curve of the depleted mantle (MORB) and enriched mantle (EMⅡ). Sr-Nd-Pb isotopic data indicate that the enriched mantle (EMⅡ) metamorphosed by subducted plate fluid might have been the source of the porphyries. In comparison with things of the Yulong ore belt, the depletion of Sr-Nd-Pb isotopes is more obvious in the northern Sanjiang ore belt, and the injection rate of asthenospheric material caused the geochemical differences between the northern Sanjiang ore belt and the Yulong ore belt. The establishment of the molybdenum-copper metallogenic belt in northern Sanjiang Region, whose center is the Narigongma-Lurige large-size molybdenum-copper deposit, suggests that there still exists a great potential for finding large porphyritic and postmagmatic hydrothermal ore deposits in this region.