The portable ultrasonic flaw detector, adopting common single rail detection trolley by manual, uses customized chassis, high-performance industrial computer and three prevention tablet computer, which ensures that the detection system can have high reliability, easy to carry even in harsh field working environment. The double scanning system can detect the rail in an all-round way, which has the characteristics of accuracy, timeliness and comprehensiveness, and the flaw detection rate can reach more than 90%.