In thermal wave NDT,the contrast is low and noise is high.In order to resolve the problem,the wavelet transformation is introduced in image enhancing step.At first,the theory of image enhancement of wavelet transformation is explained,and image enhancing process is designed.To get the best enhancing effect,threshold value,enhancing factors of enhance function are studied.The conclusions are as follows:noise reduction is influenced mainly by threshold value T;enhancing parameter K1 is relevant with enhancing effect of transition region;improvement of picture contrast depends on enhancing parameter K2.On the basis of the conclusion,threshold value T is set to be 670,K1 to be 10，K2 to be 0.1.Test image of certain composite material is processed.Compared with the original picture,the enhancing effect is quite good,which proves the availability of this enhancing method.