The risk factors of the electric power grid investment under deregulation were extensively analyzed, and were divided into probability risk factors and fuzzy risk factors according to their historical data's accessibilities. And then the probability density functions was used to describe the uncertainties of probability risk factors, while the fuzzy probabilities or fuzzy membership functions were used to represent uncertainties of fuzzy risk factors. Based on these contributions, a combined fuzzy and probability risk evaluation model for electric power grid investments was presented, in which the probability risks of the project' net present value (NPV) were quantified, and its fuzzy uncertainties were obtained by the expansion principle II. Finally, the given example proved that the model mentioned in this paper could quantify the risks of electric power grid investment in a more proper way, which could provide more information for the decision makers.