In order to solve the problem that prospect evaluation is paid much attention whereas prospect building is ignored in existing research, the inference method of alternative’s outcomes possibility set is proposed by utilizing expert voting technology. After that, the thoughts of relative comparison judgment and complementary judgment assignment are combined to construct the probability inference matrix to extract experts cognitive information effectively, and a transformation theorem is introduced to derive basic probability assignment(BPA) from the probability inference matrix. Finally, each expert is considered as an independent evidence source, then specific steps for building prospects are presented in view of the Dempster combination rule and the DSmP transformation method. A case simulation analysis is applied to describe the operational process of the presented method.