Abstract: To improve the defect detection ability of ultrasonic full focusing inspection for media with strong lateral velocity variation, a gradual multi-transducer frequency-domain full focusing method based on phase shift migration (GMTFM-PSM) is proposed. Based on the traditional ultrasonic full focusing imaging inspection, this technique employs excitation signals of multiple transducer groups, reducing the sound velocity attenuation of composite materials with strong lateral velocity variation, as well as enhancing sound beam directivity and signal strength. The phase shift migration algorithm is introduced to correct the sound velocity propagating in material, improving the migration factor accuracy and effectively reducing the influence of the complex multi-layer structure of composite materials on imaging precision. Combined with the gradual full focusing algorim, side-lobe influence is reduced and the imaging performance is optimized. The results show that compared with the traditional B-scan, SAFT-FW, and TFM-FW imaging algorithms, GMTFM-PSM algorithm reduces quantitative error by 391%, 50%, and 13% respectively, and the defect quantitative error is significantly reduced. The GMTFM-PSM method provides robust technical support for defect detection in materials with strong lateral velocity variations, particularly carbon fiber reinforced composites.