Abstract: By using the control chart to analyze statistically the hardness test data of components of the gas-insulated metal-enclosed switchgear (GIS), and using causality diagram to analyze the causes of scratch accident of GIS bearing rod, the application of control chart and causality diagram in the hardness quality management of GIS components was analyzed. The results show that the control chart can judge whether the hardness of the components is in a controlled state continuously, find abnormal phenomena in time, and take corresponding effective measures to ensure the stability of the hardness of the components. The causality diagram can comprehensively and systematically analyze the various factors that lead to the failure of the hardness of the components, identify the main reasons, and give improvement measures. Through the application of the control chart and the causality diagram, the improvement of the hardness quality management of GIS components can be effectively guided.