In supply chain, manufacturing suppliers may provide incorrect information to purchasers because of fierce market competition and privacy protection. This paper proposed a convenient method of obtaining production information based on electricity and forecasting suppliers’ Unused Production Capacity based on electricity. With fuzzy cluster-analysis technique and virtual variable-regression analysis method, the relation model between months’ electricity and product quantity was constructed. Then achieve a forecasting model of unused production capacity using gray-theory and Ordinary Least Square according to recent months’ electricity. And the example was discussed, the predicting results will provide decision-making basis for purchasers.