Abstract: For the cognition and processing of different negations of the fuzzy knowledge,paper [1]has proposed that negation of fuzzy knowledge including the contradictory negation,the opposite negation and the medium negation,and defined a new fuzzy set with contradictory negation,opposite negation and medium negation (FScom)．In order to show applicability of FScom,the fuzzy set with three different negations (FScom) was applied in the stock investment decision-making．Based on FScom,this paper introduced an approach to define the membership function of the fuzzy set and its different negations in decision rules,and discussed the threshold value of range of membership degree and its mea-ning．Finally,it discussed reasoning and realization of fuzzy decision-making in the example based on FScom and the fuzzy production rule．The final decision results were given out．The decision-making process implies that the application of FScom in dealing with practical problems with ambiguity and different negations is effective.

Key words: Fuzzy set FScom,Stock investment,Fuzzy decision,Threshold λ