By synthesizing information from geology, geochemical prospecting, and mineral deposits etc.,  the author build a GIS-based spatial database for North Bayan Har metallogenic belt in Qinghai Province. Then a new regional ore exploration model is built. And GIS-based mineral potential mapping is finished in the study area according to expert weights of evidence proposed by the present author earlier. Then prospecting potential grades of prospecting targets are divided into level A, B & C based on double integrals of posterior probabilities of every forecasting ore-bearing grid. They consist of 6 prospecting targets with level A, 10 ones with level B and 13 ones with level C.