Abstract: In this paper, a measurement method based on L(0, 2) modal guided wave signal was developed in order to detect the deformation of ultra-high molecular weight polyethylene (UHMWPE) pipeline outside the visual field. Three-layer structure and material of UHMWPE pipeline were introduced, the characteristics of single deformations and the propagation properties of various modals guided waves were analyzed. Axially deformed position was determined according to the time zero of the reflection signal on the blank plate received by the echo sensor chip, and the deformation length was determined according to the time difference of reflection signal. It is indicated that the error rates of deformation zero position and length calculated by wave form and theoretical transmission velocity based on guided wave signal are both within the acceptable range while the interference of external noise and other non-L(0, 2) guided waves is strictly controlled. This method can be used to measure the deformation and dents of the underground UHMWPE pipelines and it is convenient for operators to carry out management and maintenance.