Abstract: The signal to noise ratio of ultrasonic echoes signal was low, the echoes signal was submerged easily in ultrasonic testing, and wavelet transforms was an effective method by which the flaw echoes can be extracted. The mathematics model of ultrasonic echoes signal was established, including the flaw echoes and the noise, the traditional soft and hard threshold denoising methods based on wavelet transform was ameliorated, and a middle course method was put forward for signal denoising in ultrasonic testing. At the same time the parameters selection was also optimized with the signal to noise ratio of ultrasonic flaw echoes signal as object function. The simulation experimental results showed that this method was fit for analyzing ultrasonic signal, and it can depress noises well. This method utilized the advantage of the soft and hard threshold denoising methods and avoided their disadvantage in the farthest. Compare to the traditional soft and hard threshold denoising methods, the denoising effect was improved in a certain extent, and the signal to noise ratio of ultrasonic flaw echoes signal was improved by using this method.