Evaluating a chemical process commonly has several criteria consisting of not only the economic aspects but also social and technical ones; hence multi-dimensional evaluation becomes an important problem. Usually the different criteria, each has a distinct scale, which can hardly be unified to single one. Moreover, the frequently emerging unquantifiable parameters will make the problem more complex. Fuzzy mathematic methods have been put into use to deal with such difficulties. In order to overcome the shortcoming lying in current methods, based on the fuzzy reasoning,a multi-level evaluation approach using if-then rules is proposed in this paper. It decomposes a multi-dimensional evaluation problem to several problems belonging to different levels with fewer dimensions. The appropriate steps to establish the rule sets in different levels are provided, and a Mass Exchange Networks and a wastewater treatment plant are evaluated by using the proposed method. Satisfactory and reliable results in case studies prove the effectiveness and the efficiency of this method.