Accurate fault root cause diagnosis is essential for ensuring stable industrial production. Traditional methods

which typically rely on the entire time series and overlook critical local features

can lead to biased inferences about causal relationships

thus hindering the accurate identification of root cause variables. This study proposed a shapelet-based state evolution graph for fault root cause diagnosis (SEG-RCD)

which enables causal inference through the analysis of the important local features. First

the regularized autoencoder and fault contribution plot are used to identify the fault onset time and candidate root cause variables

respectively. Then

the most representative shapelets were extracted to construct a state evolution graph. Finally

the propagation path was extracted based on fault unit shapelets to pinpoint the fault root cause variable. The SEG-RCD can reduce the interference of noncausal information

enhancing the accuracy and interpretability of fault root cause diagnosis. The superiority of the proposed SEG-RCD was verified through experiments on a simulated penicillin fermentation process and an actual one.