Abstract: When the ultrasonic guided wave testing system is applied for nondestructive inspection of the structure and work in pulse-echo mode,the amplitude of the excitation pulse going into the transducer will be hundreds of volts while that of the received signal is from several millivolts to hundreds millivolts.According to this characteristic,an echo detection system with self-protection function was designed.The system included self-protection circuit,preamplifier,filter circuit,program-controlled amplifier,A/D converter circuit and so on.The detection process of the system was controlled by DSP+FPGA.The experimental results show that this system can achieve self-protection and precision testing,which is valuable in practice and can be used widely.