To address the challenges of extracting defect features and low signal-to-noise ratio (SNR) of conventional ultrasonic phased array in the detection of highly attenuated thick-walled structures, an ultrasonic signal processing method based on the improved sparse representation is proposed to solve the problems in this article. Firstly, the ultrasonic full matrix capture is preprocessed to obtain segmented signals and their corresponding time-frequency parameters. Building upon the parameters, the adaptive Gabor sub-dictionaries are constructed. Then, the segmented signals are sparsely decomposed and reconstructed by the improved support matching pursuit algorithm. Compared with the conventional orthogonal matching pursuit algorithm, the improved support matching pursuit algorithm combines the adaptive Gabor sub-dictionaries and lp-norm(0