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 forecasts of regional resources were finally realized. The research suggested first-level factors of mineral prediction which included strata, magmatite, and 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.