Based on the analysis about the hydrogeological conditions and engineering geological conditions, this paper makes analysis on the possible risks of the deep overlying stratum foundation and establishes the risk evaluation index system during the foundation operating period. Such methods as analytic hierarchy process （AHP） , Delphi method and fuzzy comprehensive evaluation method are adopted to make the quantitative analysis on the risk factors and establish the risk judgment model. According to the actual engineering of Taizhou Bridge, the paper evaluates the risk of the foundation during the operating period at the condition of deep overlying stratum. The evaluation results can provide the reference for the risk management of the bridge foundation durin~ the ooerating period.