A voltage sag will bring huge economic losses to high-end manufacturing enterprises. Enterprises have a strong need for premium power, and their willingness to invest in premium power is gradually increasing. However, there is no way to choose the best premium power investment scheme. In order to solve this problem, a multi-information fusion premium power investment decision-making method based on evidence reasoning theory is proposed. The criteria system of premium power investment decision-making is established by deeply analyzing the influence factors of premium power investment decision-making. The weight of the index is obtained by combining subjective and objective weights, unifying the two weights and reducing the subjectivity of the weights. Finally, based on a basic probability function composed of weights and rank belief degrees, multiple information fusion is performed using evidence reasoning theory to optimize the premium power investment scheme. Through a case analysis of a semiconductor manufacturing enterprise, it is proved that the combination of subjective and objective combination weighting and evidence reasoning proposed in this paper can make effective decision-making on premium power investment schemes, and that this has better practicality. This work is supported by Science and Technology Project of China Southern Power Grid Co., Ltd. (No. GZHKJXM20170141).