Abstract: Urban road defects are highly concealed, and traditional detection methods suffer from issues such as low efficiency and high destructiveness, making them difficult to meet the increasing demand for road maintenance. Three-dimensional ground-penetrating radar (GPR) technology, as an efficient, economical, and rapid non-destructive testing method, possesses significant advantages. To evaluate its applicability and reliability in detecting concealed defects on urban roads, this study, based on a clear understanding of the detection principle of 3D GPR, takes a road in a city in Jiangxi Province as the research object. It employs 3D GPR technology to analyze the causes of concealed defects such as poor interlayer bonding, voids, overall plate subsidence, damage to lower plate joints, and cracks in the lower plate mesh. Comparative verification is conducted through on-site coring inspection. The results indicate that the 3D GPR achieves a recognition accuracy of 92.9% for invisible defects on urban roads. However, its performance varies in recognizing different defects, suggesting that the radar's recognition capability differs among defects formed by various mechanisms. This highlights its superiority in early warning of high-reflectance defects and its core value in enhancing maintenance quality and decision-making scientificity. It also provides reliable technical support for the "early treatment of hidden defects" on urban roads.