In　this　paper,　a　soft　threshold　method　based　on　a　wavelet　transform,　and　a　decomposition　reconstruction　method,　are　proposed　to　preprocess　photoplethysmograph　(PPG)　signals.　First,　the　soft　threshold　method　is　applied　to　remove　the　high-frequency　noise.　The　wavelet　decomposition　and　reconstruction　method　are　then　used　to　adjust　the　baseline　drift　in　the　PPG　signals.　The　aim　is　to　obtain　a　higher　signal-to-noise　ratio　and　smoother　PPG　signals.　Finally,　the　validity　of　the　proposed　signal　preprocessing　method　is　verified　using　the　general　indicators　of　RMSE,　the　smoothness,　and　the　starting　point　variance.　©　2021　IEEE.