Abstract: To the problems of ascertaining nonmembership functions of Intuitionistic Fuzzy Set（IFS），a technique for ascertaining nonmembership functions based on contrast average-fixing method is proposed，whose arithmetics and steps are presented in detail with the demonstration of rightness in theory.At last，the validity and practicability of the technique are checked by providing an example analysis in applications.Researches show that the proposed arithmetic has solved the problems of technique for ascertaining nonmembership functions of IFS effectively，who have the trait of fixing order according to different attributions.

Key words: intuitionistic fuzzy set, nonmembership functions, Intuitionistic Fuzzy Set（IFS） in normalization, contrast average-fixing method, target recognition

摘要： 针对直觉模糊集（IFS）非隶属度函数难以确定的问题，提出一种基于对比平均法的IFS非隶属度函数确定方法，给出了详细的算法步骤，并从理论上证明了其正确性。最后，通过实例分析从应用上验证了算法的有效性与实用性。研究表明，该算法可有效地解决元素依属性具有先后顺序特性的一类IFS非隶属度函数确定方法的问题。

关键词: 直觉模糊集, 非隶属度函数, 正规直觉模糊集, 对比平均法, 目标识别