Based on ultrasonic principle, digital ultrasonic flaw detector MFD500B with 320*240 TFT LCD, it can test, orient, evaluate and diagnose various flaws such as crack, lard, air hole in workpiece’s interior swiftly and accurately without any destruction. It can be used in Laboratory as well as in engineering filed. With range of 0-9999mm, it can meet the requirement for general defect inspection in manufacturing industry, metallurgical industry, metal processing industry, chemical industry and so on. Low power design with large capacity and high performance lithium battery module, it can be long standby for months. High quality with low price, it is the first choice for the practical economic model for ultrasonic testing equipment.