The intelligent and hand-held ultrasonic thickness gauge is controlled by a microprocessor, which can measure thickness and sound speed of various materials quickly, accurately and without damage by ultrasonic measurement. This instrument is capable of accurate measurement for different materials or parts in industrial production, as well as monitoring pipelines and pressure vessels of production equipment, and corrosion degree of various parts in use. It can also be widely used in manufacturing, metal processing, commodity inspection and other testing areas. Any material that allows ultrasonic to transmit at a constant speed and that is distinguishable from waves reflected from the back side is applicable to this instrument.