In allusion to the shortage of traditional analytic hierarchy process (AHP) in the determination of weight coefficient, a threat evaluation algorithm based on the principle components analysis, fuzzy theory and AHP was proposed in the article. The subjective and objective factors were comprehensive considered. The importance of each index in index layer obtained by the principal components analysis method was used to gain the judge matrix in the AHP, then the relatively weight of index layer to target layer was obtained. The threat attribute value of different targets in scheme layer was gained by establishing fuzzy membership function. Then, the total combination weight of each target was gained. The simulation proved that the result obtained was objective and reasonable