Abstract: The internal arc fault test is a compulsory test item of high voltage switchgear (when applicable), the internal arc fault energy is large, and the impact pressure on the switchgear and sheet and panel cover plate is large. Because of the light weight of the arc and the complexity of the arc occurrence, there are many uncertainties in the test. This paper summarizes the phenomena and problems of more than 30 internal arc fault tests in the past ten years, analyzes and summarizes the pressure calculation, arc energy, arc root transfer, switch trip and other aspects, combined with customer demand and practical application. The design of the switch cabinet against internal arc fault is discussed in the design of pressure release channel, pressure relief cover plate, cabinet top protection and ventilation hole.