Expert system based on expert knowledge is one of the most common technologies in chemical fault diagnosis.Knowledge acquisition is the bottleneck of expert system

so knowledge extraction is the key technology of expert system.In this paper

an extracting knowledge technology based on gene expression programming (GEP) for fault diagnosis of chemical processes was presented.Fuzzy processing of the data was performed with the ambiguity function

and then from the database the anomalies and the reasons of these anomalies were identified by using GEP evolution properties.Therefore the knowledge rules were obtained which could be used in fault diagnosis.Practical case study showed that the technology combined with experts in the field could effectively extract fault diagnosis knowledge

and could be used as a knowledge acquisition tool in expert system for fault diagnosis of chemical processes.