When axisymmetric guided wave modes propagate to the defect location in a circular pipe, the uneven reflection of energy caused by the defect generates non-axisymmetric guided waves. The propagation characteristics of these waves have a quantitative relationship with the position and size of the defect, which can be used to detect pipeline defects. However, the propagation characteristics of non-axisymmetric guided waves generated by defects in polyethylene (PE) pipes are currently unclear. To address the issue of cracking at heat-fused joints in buried PE pipes, this study investigates the energy distribution patterns of non-axisymmetric longitudinal guided wave L(M,2) in PE pipes and utilizes these patterns to detect and evaluate defects at heat-fused joints. First, the feasibility of exciting non-axisymmetric guided waves in metal pipes using a discretely distributed piezoelectric array was first theoretically investigated, and the number of piezoelectric elements in the array was optimized. Next, a method for defect-induced non-axisymmetric guided waves was proposed, and simulations confirmed that the generated non-axisymmetric guided waves could be used to detect and evaluate defects. The optimized piezoelectric array was then applied to excite non-axisymmetric guided waves in PE pipes, and their axial propagation characteristics were quantitatively analyzed. Experiments verified that the propagation characteristics of defect-induced non-axisymmetric guided waves in PE pipes aligned with predictions. Subsequently, experiments on PE pipes with heat-fused joints demonstrated that intact joints do not generate non-axisymmetric guided waves. Finally, experiments on buried PE pipes showed that by analyzing the non-axisymmetric guided waves generated by defects at heat-fused joints, it is possible to determine the presence of defects and assess their circumferential locations.