Abstract: Because conventional non-destructive testing methods cannot effectively detect defects in welds of pipeline,the expansion method combined with the time reversal method to detect different types of defects in the weld was proposed.Firstly, the axial position of the weld was determined by the displacement time history curve of the guided wave propagating on the pipeline, and then the expansion method was used to determine whether there are defects in the weld and the circumferential position of the defect. For the small defects in the weld which is difficult to identify, the time reversal method was used for energy focusing processing. The numerical simulation results show that the combination of expansion method and time reversal method can effectively identify defects in welds.