The ISO 16809 standard specifies the method of ultrasonic thickness measurement in nondestructive testing. The standard is suitable for the measurement of the thickness of materials or components using ultrasonic technology, especially in the thickness evaluation of metals, plastics, composites and other materials. Ultrasonic thickness measurement calculates the thickness of materials by emitting ultrasonic pulses and receiving their reflection signals, which has the advantage of not damaging the material itself. The standard describes in detail the use of instruments, measurement process, accuracy requirements and Data analysis methods to ensure Reliability and accuracy of measurement results. This method is suitable for complex structures and parts that cannot be directly contacted. It is widely used in quality control and testing in engineering, manufacturing and maintenance.