To slove the problem in the transformation of basic probability assignment to decision-making probability, this paper proposed a novel transformation method based on correlation degree. The correlation degree between basic probability assignment of singleton proposition and decision-making probability was used to evaluate the transformation method, and the decision-making probability of each proposition was achieved by linear combination, which was the transformation method of decision-making probability based on proportional belief and proportional plausibility. The proposed method was compared to the other usual methods with an example. The experimental result shows that the proposed method is more reasonable and effective.