To improve the accuracy of positioning and quantifying delamination defects in carbon fiber reinforced polymer, a precise frequency domain total focusing method three-dimensional imaging technology based on two-dimensional equivalent sound velocity mapping is proposed. This technique first changes the division standard of the sub-matrix from the excitation point position to the excitation-receiver spacing, and obtains a new full matrix data. Then, the transformed two-dimensional sub-matrix is transformed into the frequency domain. According to the change of depth and spatial frequency, an accurate two-dimensional equivalent sound velocity mapping is derived to match the transceiver separation signal in the sub-matrix data, and the sub-matrix frequency domain reconstruction diagram is obtained by combining the angular spectrum operation. The sub-matrix focusing image is obtained by inverse fast Fourier transform and fused to obtain the full focusing image. Finally, the final three-dimensional image is obtained by using multi-plane threedimensional reconstruction technology. Compared with the traditional F-TFM and F-SAFT algorithms, the results show that the proposed algorithm effectively suppresses the generation of side lobe effect. The quantitative error of double defect spacing is reduced by 20. 31% , and the quantitative error of defect width is reduced by 5. 43% and 6. 3% , respectively. When the defect depth and the double defect spacing change, the higher detection sensitivity can still be guaranteed.