Abstract: To the confidence factors spreading in IFS approximate reasoning，the related formulas for finding the confidence factors of conclusions are exposed in this paper.First，with confidence factors been introduced，the effects of confidence factors spreading abroad in rules on those of conclusions are analyzed.To the IFL approximate reasoning with confidence factors，including the generalized modus ponens，generalized modus Tollens，generalized hypothetical syllogism on IFL，the related formulas are exposed.The correctness and validity of the proposed formulas are verified in a particular instance．

摘要： 针对直觉模糊近似推理中的可信度传播，提出计算结论可信度的相关算法。首先介绍了可信度因子的概念，分析了规则中的可信度因子传播对结论可信度的影响。然后针对直觉模糊近似推理的三种基本模式（取式、拒式、假言式），给出了计算结论可信度值的相关公式，最后通过实例验证了算法的正确性。