Abstract: The fracture phenomenon of the conductor spacer of the 500 kV Mengzhao I line is studied. Macroscopic inspection of the appearance and fracture position of the fractured spacer reveals casting defects such as large-sized pores on the fracture surface. Microstructural observation reveals more point and hole defects on the surface of the fractured spacer plate sample, the surface of the unfractured spacer plate sample is normal. Scanning electron microscope analysis shows that the fracture is characterized by brittle fracture, and there are many casting defects such as holes in the fracture structure. Due to the casting defects of the spacer connecting plate, the mechanical properties of the connecting plate are reduced. Under various stress conditions such as the self-weight of the wire and the reaction force between components for a long time, the connecting plate forms cracks and expands at the stress concentration part, eventually leading to its fracture.