Abstract: Through extensive spectral evaluation studies in TOFD testing, it has been discovered that many relevant indications caused by common base metal linear indications (segregation) and non-relevant indications caused by excessive assembly gaps between probes and wedges share the same two-dimensional morphological characteristics, leading to a high risk of misjudgment and missed detections. Grounded in practical engineering projects, this paper analyzed the segregation of base metal and weld composition. Additionally, it integrated other detection methods and on-site dissection verification to investigate the impact of linear indications (segregation) on TOFD detection and rating. Through this analysis, the fundamental characteristics, potential causes, judgment methods, and evaluation principles of linear indication (segregation) maps were identified. This enhanced the accuracy and objectivity of TOFD detection data evaluation, streamlined the TOFD detection process, and shortened the equipment manufacturing period.