Weight allocation is the key in multiple attributes decision making (MADM) procedure. Because of the complexity of decision problems, it is difficult to embody the subjectivity of the people in the decision-making process if using objective method only. Meanwhile, it is difficult to reflect the essence of the problem objectively if only according to person's subjective judgment. Flexible decision holds better adaptability. Therefore, this paper proposed a flexible dynamic weight decision scheme (FDWDS). On the basis of the data type analysis, attributes type and the completeness, the accuracy of related knowledge information, the influence of objective, subjective and the preference of decision makers for flexible weight allocation, the weight could dynamically adjust according to the analysis of different objects. Finally, through the simulation experiment its applicability and the rationality of weight allocation were verified.