To accurately predict the location and size of defects in the pipeline, a synthetic aperture guided wave imaging algorithm based on frequency wavenumber domain is proposed. And the principle of explosive reflection imaging is also utilized. The T ( 0,1) mode guided wave is excited in the pipeline by magnetostriction. The collected echo signal is subjected to two-dimensional Fourier transform and angular spectrum operation to reconstruct the sound field in the frequency domain. Finally, the focus imaging in the target area is realized by using the inverse Fourier transform. The imaging results are verified by experiments and compared with the original B-scan results. Results show that the side lobe effect is effectively controlled by the proposed algorithm. The imaging resolution is improved about 30% and the quantitative error is reduced by 26. 1% . The affection of the axial position, the depth and the inclination angle of defects are also studied. By using the algorithm to reconstruct the defect image, the detection accuracy is only affected by the absolute size of the circumferential defects and the detection of circumferential surface defects has a high sensitivity.