Abstract: According to the thin copper rod of  2.5~15 mm, the method by combination of the rayleigh wave of pulse-echo and the longitudinal wave of penetration is adopted.the testing problem of the thin copper rod of 2.5 mm~ 15 mm is solved very well,and the ultrasonic auto-testing system for thin copper rod is developed. The system consists of several functional units, such as the upper computer(PC unit),the lower computer(Single Chip Microcomputer unit),the pulser/receiver, transducer and the mechanical unit.The upper computer and lower computer can communicate with each other by RS232,which accomplish the system controlling and data collecting.The experiment shows that the ultrasonic atuo-testing system can accomplish qualitative and quantitative testing for thin copper rod of  2.5~15 mm,which the diameter of the artificial blat-bottom hole is 0.5mm and the length of it is 1/4D.