Structural cracks are widely distributed in current expressways, yet there is a lack of targeted evaluation methods. To achieve a quantitative assessment of structural cracking conditions in semi-rigid base asphalt pavement, this study first analyzed the development process of structural cracks based on coring tests. Subsequently, combined with non-destructive testing technology using 3D ground-penetrating radar and on-site coring experience, the morphological characteristics of structural cracks at various development stages were analyzed, and the cracks were classified into mild, moderate, and severe levels according to their development layers. On this basis, road section-level evaluation indicators, namely structural cracking spacing (S_D) and structural cracking condition index (I), were proposed, with their calculation methods and a five-level evaluation standard (excellent, good, medium, poor, and very poor) clearly defined. Verified through engineering applications on multiple expressways, this grading evaluation method could accurately reflect the actual status of structural cracks in semi-rigid base asphalt pavement and has certain guiding value for maintenance construction.