Abstract: The Bohai Sea has a superior geographical position. The development of its marine economy asks urgently for the support of geological environment data. Most present studies usually are concentrated on some individual seas, and lack of the systematic thinking of different seas using actual testing data. Based on the available data of environmental geological factors in marine regional geological survey since 2008, The Bohai Sea was divided into grid cells and the characteristic parameters of its main environmental geology factors were quantified. An indicator system of the evaluation of the geological environment stability was established based on the topographic or ground environmental change, uneven bearing stratum, and active tectonics. The geological environment stability in the study area was quantitatively evaluated by using expert-analytic hierarchy process and fuzzy mathematics. Results suggest that the geological environment stability in Bohai Sea was divided into five grades: poor, relatively poor, medium, relatively good, and excellent. The stability in most of Bohai Sea is generally in good condition at the present. The regions in poor and relatively poor grades of stability accounts for 10%, particularly in the adjacent area of the Yellow River Delta, where the unstable environmental geology factors active faults, earthquake epicenter, shallow gas and the factors related to the tide are comparatively dense, with relatively large hazard. This study is valuable for future exploitation and utilization of natural resources, eco-environment conservation in Bohai Sea. Meanwhile, the quantitative evaluation method of this study provided a reference for the study of marine environmental geology.