The evaluations on the same factor from different experts, based on AHP, are not identical, and some even far cry, because the evaluation may be effected by the knowledge, experience and emotion of the experts. To remedy this shortage, this paper established a hierarchical analysis model based on entropy. In the model, entropy value represents the uncertainty of the results. And entropy weight reflects the contribution of every expert in the assessment. Then comprehensive combination weights of the factors are determined, reflecting the importance of every factor. Applying the method, the risk factors in some bridge construction were analyzed, and, the conclusion has important significance for correct risk countermeasures and smooth construction.