In order to overcome the defects of stronger subjectivity of common assessment methods of marine ecological environmental assessment, the entropy weight model was introduced. In the comprehensive assessment, because of different influence degrees of each index to the comprehensive assessment results, different improved measures can be adopted to increase policy ability. As Shannon information entropy has the advantages of objectivity and adaptability in determining weight value, it was applied to determine the weight value of each index in the comprehensive assessment model. Then the optimal and worst indexes were selected based on a double base point model. Through comparing the distance between the scheme point and double base points, the result of comprehensive assessment can be obtained. Then the model was employed to assess the ecological environment of a bay of China. Application results show the efficiency of this method.