With the popularization and application of automation and intelligence technology in substation, the foundation of intelligent inspection is laid, but at present, the protection hard-pressed plate of secondary equipment still mostly adopts manual on-site checking, which has the problems of low checking frequency and insufficient traceability of proofreading process. Therefore, this paper proposes an intelligent recognition method of the operating state of the press plate based on image content recognition. The OTSU algorithm based on spatial domain information is first used to segment the threshold to eliminate the influence of illumination uneven shadow area. On this basis, the minimum rectangular area of the plate switch is detected based on the Graham minimum external rectangular algorithm, and the area size is identified .