Abstract: Aiming at the problem that the hard threshold function was discontinuous at the threshold and the soft threshold function was a continuous function but had a fixed deviation, after analyzing the advantages and disadvantages of the hard threshold function, the soft threshold function and several representative improved threshold functions, a wavelet denoising algorithm for the improved threshold function was proposed, and the MATLAB software was used for simulation verification. The experimental results showed that proposed improved threshold function had a good denoising performance. Further applying this algorithm to the denoising of TOFD images, the results showed that the proposed improved threshold function had good application performance in TOFD detection.