The selection of web services according to different quality of service (QoS) is one of the most important decision issues for which complex considerations are involved. In many cases, the values for the qualitative QoS criteria are often imprecisely defined or acquired. Moreover, it is also not easy to accurately quantify the weight of each QoS criterion since human judgments including preference are often vague. In this paper, we apply the fundamental principles in the fuzzy set theory and model the decision making problem as Fuzzy Multiple Criteria Decision Making (FMCDM). The main contribution of this paper is to balance the subjective weight which reflects human rating and objective weight which represents reliability of evaluation criteria to form a synthetic weight. The detailed analysis of the synthetic weight for QoS-aware web service selection application is also presented.