Based on the geological and mineral geo-database, the authors analyzed the metallogenic conditions of porphyry molybdenum-copper deposits in northern Sanjiang region by means of GIS. A prognostic model for regional ore deposits was established, and the factors of mineral prediction were extracted and assigned values by Graded-WOE. The favorable prospecting areas were delineated, and the quantitative forecast of regional resources were finally realized. The research included several aspects, and the weighing of prediction included strata, magmatite, structure, mineralized anomalies and other related quantitative factors. Firstly, the geological and mineral geo-database based on the platform of Mapgis and Arcgis of northern Sanjiang region was established, which included regional geological data of the geological map, gravity, air magnetic force measurement, geochemistry, remote sensing and mineral data. This database constitutes the basis of regional mineral prediction. Secondly, the research probed into the metallogenic conditions of porphyry molybdenum-copper deposits in northern Sanjiang region by comprehensive handling of mineral information and analysis of the conditions of mineral deposits and the ore-forming indicators. The research suggested first-level factors of mineral prediction which included strata, magmatite, structure and mineralized anomalies, 19 related factors and 24 relevant characteristic variables. The authors analyzed characteristic variables by Graded-WOE, and then converted them into the values of posterior probability of strata, structure, magmatite and mineralized anomalies. Two favorable areas, i.e., Narigongma-Dongmozhazhua and Aduo-Jieduo, were delineated by the values of posterior probability. There are 5 target areas of Grade-A molybdenum-copper deposits, 4 target areas of Grade-B molybdenum-copper deposits and 4 target areas of Grade-C molybdenum-copper deposits. Using the bundance model, it is estimated that the quantity of copper in this region is 7 412 730 t and that of molybdenum is 8 566 180 t.