This paper is aimed to present a fuzzy decision making approach thorough combining fuzzy expert system and fuzzy Entropy to deal with the supplier assessment and to encounter the uncertainty in this environment. Although decision making in supplier selection is unstructured and consisted of many criteria such as price, quality, delivery time, flexibility, and technical capability, in this paper, the criteria are categorized and linguistic variable is used to reduce the uncertainty of decision making. Inputs of the designed expert system are calculated by fuzzy Entropy method, and finally, an example is shown to highlight the procedure of the proposed method.