In　the　inspection　test　on　steel　strands　by　using　ultrasonic　guided　waves,　the　lowest　longitudinal　mode,　L(0,　1)　mode,　is　excited　and　received　by　a　pair　of　developed　magnetostrictive　sensors　in　a　seven-wire,　17.80　mm　nominal　diameter　steel　strands.　Then,　the　signal　is　denoised　by　using　the　method　of　multi-level　discrete　wavelet　decomposition　and　single　branch　reconstruction.　The　daubechies　wavelet　of　order　40　is　used　as　the　mother　wavelet　for　the　decomposition.　This　wavelet　denoise　method　improves　the　signal-to-noise　ratio.　Furthermore,　a　steel　strands　with　3.00　mm　depth　notch　on　peripheral　wire　is　inspected,　the　information　of　the　defect　is　extracted　from　the　signal　by　using　the　wavelet　denoise.　This　signal　processing　method　of　wavelet　denoise　provide　foundation　for　application　of　ultrasonic　guided　waves　technique　to　health　monitoring　of　steel　strands.