The ISO 16413 standard specifies the relevant requirements for the evaluation of film thickness, density and interface width using X-Rays reflectors. It details the technical requirements of the instrument, alignment and positioning methods to ensure accuracy and conformity during testing. The standard also covers the steps of data collection, analysis and reporting to help users accurately measure the critical physical properties of thin films, widely used in materials science, semiconductor manufacturing and other fields. The standard provides systematic guidance for the precise characterization of thin film materials, ensuring Reliability and comparability of test results.