针对定性故障诊断系统的固有缺陷，利用模糊数学知识，在符号有向图上加入定量信息，形成定性定量模型，通过计算和比较被诊断模式对已知故障类型的模式的隶属度来确定系统的故障。该方法比较充分地利用了系统被监测参数的数值资源，对故障模式具有较强的识别和区分能力。 Aiming at the inherent flaws of qualitative fault diagnosis system, fuzzy mathematics knowledge is used to add quantitative information to the digraph to form a qualitative and quantitative model. By calculating and comparing the membership degree of the diagnosed mode to the known fault type, malfunction. The method makes full use of the numerical resources of the monitored parameters of the system and has strong ability of identifying and distinguishing fault modes.