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In the area of fault analysis, SDG (signed directed graph) models can be used to describe the system states and the fault propagation paths which are the composition of qualitative deviation from the normal state. In control systems, besides the natural relations caused by the physical properties, the forced control actions determine the dynamic properties of the systems, which cause the particularity of SDG model-based analysis. In this paper, the SDG description and the analysis methods of fault propagation in control systems are presented, and the typical cases like PID control, feedforward control, split-range control, cascade control etc are illustrated. A graphical analysis method is proposed to substitute the algebraic methods based on equations. These results can be expanded to various control systems and even be applied to large-scale industrial systems by the combination and connection of several basic elements.