At present, researchers use the geochemical block theory to predict amount of mineral resources based on the geochemical data. Although they take the influences of formation and structure besides the ore material source into account, the application remains in qualitative stage. On the foundation of geological background researches the authors come to the conclusion that the enrichment factors, namely formation and structure are two necessary conditions for the ore-forming material base. Finally, the authors set up the ore prospecting probability-geochemical block ore prospecting method, and use it to quantitatively assess the amount of boron ore in eastern