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.