The ISO 9220 "metallic coatings - Coating thickness measurement - Scanning Electron Microscope method" standard specifies a method for measuring the thickness of metallic coatings using the Scanning Electron Microscope (SEM). This method uses high-resolution images from the Scanning Electron Microscope to analyze the interface between the coating and the substrate, resulting in accurate measurement of coating thickness. The standard describes in detail the instrument setup, sample prepative, measurement process and data processing requirements to ensure measurement accuracy and conformity. The Scanning Electron Microscope method is suitable for a variety of metallic coatings, especially in high-precision testing. This standard provides a reliable and non-destructive testing method for coating mass control and verification, and is widely used in high-tech industries such as aviation and automobiles.