The invention relates to the field of electricity transactions, in particular to an electricity transaction monitoring risk index evaluation method based on unascertained rational numbers. The method comprises the steps of firstly, performing integrated credibility modeling for electricity market experts, obtaining integrated credibility of the experts participating in the marking; secondly, the experts marking secondary indexes by reference to index values of the secondary indexes; thirdly, based on the credibility and marks given by the experts, obtaining marks, which belong to unascertained rational numbers, of the secondary indexes; and fourthly, combining the weights of the secondary indexes and corresponding marks, calculating the marks of primary indexes that the second indexes belong, and calculating the mark of a total goal on the analogy of this. The invention has the beneficial effects of being capable of electricity transaction monitoring risk index evaluation by using the unascertained rational numbers, acquiring a variety of possible values of the evaluation results and corresponding credibility, and achieving risk index quantification and effective risk monitoring.